SPACE NEWS
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SPACE NEWS
of Extra-Solar Space
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. . See also: Planetary Space News.)
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. . Note, too, that there's 8 times more H floating free than there is in stars.
. . This is the clearest explanation I've found on dark energy & the expansion of the universe (eXit to return).
* My (prob'ly wacky) idea: the so-called anti-gravity now
known to exist between galaxies --pushing them apart &
speeding up the expansion-- must also push IN on the edges of all widely-separated galaxies. This would make them more compact & would rotate faster, making it seem like they're heavier than they are. i.e. they don't rotate fast because there's a heavy center --BH or not, but because it's Anti-Grav "pushing", rather than gravity "pulling". I wonder if this has been inserted into their calculations.
Neutron star gravity: 300,000 times that at Earth.
If the sun collapsed into a singularity, its event horizon
would measure approximately 3 km across. If Earth followed
suit, its event horizon would only measure 1 centimeter.
For perhaps its first million years, the Universe was small and dense enough that sound waves could travel through it [!] --so efficiently, in fact, that they moved at about half the speed of light! 500,000 X as fast. & the Universe was so small then, sound cuda gotten across quickly.
The Milky Way in its entirety spans more than 100,000 light-years.
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Feb 2003: a joint NASA–Princeton University satellite, the Wilkinson Microwave Anisotropic Probe, produced a high-resolution map that captured the oldest light in the universe. This ancient light, called the cosmic microwave background, is the cooled remnant of the Big Bang. This has accurately determined the age of the universe -—with just a 1% margin of error: 13.7 billion years old.
. . The Earth is 4.6 billion years old.
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NEWS:
Dec 23, 06: A debris disk spied recently around a distant dead star is likely the remains of a planetisimal that was vaporized when the star died, scientists say.
. . The discovery could be a sign of what will happen in the Solar System in a few billion years. Because the crushed planetisimal was probably gravitationally lassoed in by one or more planets, the finding also provides evidence that planetary systems can form around massive stars.
. . The discovery of this disk around the white dwarf is good evidence of the existence of planets, according to G?nsicke. "While we haven't found a planet directly, we have quite strong indirect evidence that there must be a planet."
Dec 20, 06: European scientists launched a satellite today to seek out new Earth-like planets beyond the solar system and to explore the interior of stars. It's capable of detecting planets smaller than is currently known --some maybe just a few times the size of Earth and rocky. It will monitor about 120,000 stars for tiny dips in brightness that result from planets passing across their faces. "That is, they'll be somewhat bigger than the Earth, but they'll be made of rocky material able to sustain an atmosphere, and probably provide the sort of environment in which life could form.
. . The multinational mission will also study the stars directly to uncover more about their interior behavior.
. . It relies on the chance alignment of the star and the planet with Earth. As a consequence, Corot must keep an eye on more than 100,000 stars. They expect to find between 10 and 40 rocky objects slightly larger than Earth, together with tens of new gas giants similar to our Jupiter, in each star field they observe. Every 150 days, Corot will move to a new field and begin observing again.
. . Corot's instrumentation is also designed to detect the subtle variation in a star's light caused by sound waves rippling across the surface. These waves are the equivalent of seismic waves on the Earth. By studying these "starquakes", astronomers can gain a detailed insight into the internal conditions of the star.
. . The satellite is the first of a number of spacecraft that will hunt and study distant planets over the next few years.
Dec 21, 06: As a parting swan song to the universe, most massive stars explode in a tremendous burst of light and energy when they die. But astronomers have detected a new class of enigmatic stars that appear to fade away quietly, and in the dark.
. . Until now, scientists had thought stars expire in only one of two ways. When stars up to eight times more massive than our Sun run out of fuel, their outer layers slough away to leave behind a smoldering stellar corpse, called a white dwarf.
. . Heftier stars above this mass-threshold die more violently. When these stars run out of fuel, their cores collapse, triggering titanic explosions called supernovas that can fling several solar masses worth of material into space. After the blast, what's left in place of the star is either a neutron star or a black hole.
. . One possible explanation is that some massive stars bypass the supernova phase completely in death, letting out only a long gamma ray sigh before collapsing immediately into a black hole. In this scenario, "all the material that is usually ejected in a supernova explosion would then fall back and be swallowed."
. . Another possibility is that the new type of long GRB is produced by a cosmic merger of some sort. For example, collisions between two neutron stars or a neutron star and a black hole also produce GRBs. However, these GRBs are typically much more fleeting, lasting less than 2 seconds, and they also tend to be much less energetic.
Dec 20, 06: Astronomers might have seen the very first stars in the universe. If so, these are incredible stars, some 1,000 times as massive as the Sun. The alternative is just as interesting: The objects might be early black holes consuming gas voraciously and spitting out radiation like crazy as nascent galaxies form. "We are pushing our telescopes to the limit and are tantalizingly close to getting a clear picture of the very first collections of objects."
. . The light comes from objects that are more than 13 billion light-years away. That means the light began its journey more than 13 billion years ago. The universe is just a smidgeon older, at 13.7 billion years, and astronomers are pretty sure it took a few hundred million years for the matter of the Big Bang to spread out enough, and cool, to allow the first stars to form.
. . A little math therefore shows that these newfound objects are indeed the infants of the universe. But what are they? If they are stars, they are about 10 times more massive than theories suggest the first stars would have been.
. . The mysterious objects are in clusters. If they are each stars, then the clusters might be the first mini-galaxies. And if so, each apparently has a mass that's less than a million suns. Our Milky Way, by contrast, holds the mass of about 100 billion suns and is thought to have been built up by mergers of smaller galaxies-perhaps like those the astronomers now think they might be seeing.
. . The light measured in the new study is thought to have started as ultraviolet and optical light, and it has been stretched over time to infrared. Kashlinsky's team calls it the cosmic infrared background and describes it as a diffuse light from the early time when structure first emerged.
. . The problem in making sense of it all lies with the fact that the observations are not clear-cut. The scientists had to remove light from foreground stars and galaxies, and then study fluctuations in what is a relatively diffuse light.
Dec 14, 06: New findings suggest that as the Solar System was forming in a corner of the Milky Way galaxy out of a vast spinning disc of gas and dust, it mixed materials over great distances of space rather than coalescing in a more orderly fashion.
Dec 14, 06: European Southern Observatory (Eso) officials have given approval for a detailed design study of the European Extremely Large Telescope to proceed. The telescope's mirror will be 42m in diameter --four times bigger than any other currently in existence.
. . Eso operates the 8.2m Very Large Telescope (VLT) at Cerro Paranal in Chile, which has been described as a "discovery machine". An average of 1.5 scientific papers published each day are based on observations carried out at the VLT.
. . Dr Cesarsky says the design will require "a complete rethinking of the way we make telescopes". The primary 42m mirror is to be composed of 906 hexagonal segments, each 1.45m in size, while the secondary mirror could be as large as 6m in diameter.
. . In order to compensate for the fuzziness of stellar images due to atmospheric turbulence, the telescope needs to incorporate "adaptive" mirrors. A tertiary mirror, 4.2m in diameter, relays the light to the adaptive optics system, composed of two further mirrors. One of these is a 2.5m mirror able to distort its own shape a thousand times per second with the help of many actuators, the other is 2.7m in diameter and makes final image corrections possible. This five-mirror approach will, Eso hopes, result in an exceptional image quality.
. . The site of the E-ELT is not yet fixed; Eso plans to make a decision by 2008.
Dec 11, 06: A monster star thought to be among the most massive in our Milky Way galaxy is actually slimmer than expected because it's actually a pair of twins, astronomers announced today. The stellar find is part of a study to determine the upper mass limit for stars.
. . Researchers once believed the star --known as Pismis 24-1-- loomed large with a mass between 200 and 300 times that of the Sun. But more accurate measurements by the Hubble Space Telescope found not one, but two stars in Pismis 24-1's location, effectively cutting the estimated weight in half to about 100 solar masses.
. . The team also managed to gauge the mass of a third nearby star, dubbed Pismis 24-1, and pegged that object at about 100 solar masses. It's possible that Pismis 24-1 may include a third star based on some ground observations, Hubble researchers added. If true, each of the three stars would average about 70 stellar masses, but remain on the Top 25 roster of the Milky Way's most massive stars.
. . For every discovery of a 65-solar mass star, some 18,000 Sun-mass stars are formed, they added. The lifecycle of a 65-solar mass star ends after just three million years, though a Sun-mass star can burn for more than 3,000 times that. Our own Sun is considered middle-aged at 4.6 billion years old.
Dec 6, 06: The Arecibo radio telescope, with its signature 1,000-foot reflector dish set in a jungle-like landscape, is best known as a setting in "Contact", a 1997 Jodie Foster movie.
. . At the world's largest radio telescope, astronomers searching for asteroids on a collision course with Earth are bracing for a more worldly threat: The steepest budget cuts and first layoffs since the observatory opened in 1963.
. . Managers are warning staff and outside astronomers to prepare for a leaner future, with fewer research projects and less telescope time available as they finish a costly repainting job amid a looming cut in U.S. government funding. "The whole world loses if funding is lost for Arecibo", said Lance Benner, a research scientist at NASA's Jet Propulsion Lab. He uses the telescope to track near-earth asteroids. "We're a very inexpensive form of insurance for the whole planet."
. . The telescope is so prized that astronomers let out a collective shudder in November when a review panel recommended the U.S. cut 25% of the observatory's $10.5 million astronomy budget next year and consider eliminating it entirely at the end of the decade. The panel suggested that the private sector or overseas institutions could pay part of Arecibo's costs.
. . Future programs include the U.S. share of an international radio telescope under construction in the Atacama Desert of Chile. When it opens around 2011, it will be the largest observatory ever built.
. . Cornell officials plan to lobby Congress to maintain the funding.
Dec 6, 06: A giant black hole has been caught in the act of guzzling a star in a galaxy 4 billion light-years away, scientists using an orbiting NASA telescope said. For the past two years, scientists have monitored the dramatic events as the star, residing in a galaxy in the Bootes constellation, was ripped apart by the black hole.
. . Scientists used NASA's Galaxy Evolution Explorer, an orbiting telescope sensitive to two bands of ultraviolet wave lengths, to detect an ultraviolet flare coming from the center of a remote elliptical galaxy.
. . Only once every 10,000 years will a star pass close enough to a (galaxy's) central black hole to be ripped apart and swallowed in this manner", Gezari said. It is believed that super-massive black holes are located at the core of every galaxy. They believe that parts of the star swirled around and then plunged into the black hole, which sent out the bright ultraviolet flare that the satellite detected. Scientists continue to use the telescope to observe the ultraviolet light as it fades while the black hole snacks on the final table scraps from the devoured star.
Nov 30, 06: Humans must colonize planets in other solar systems traveling there using "Star Trek"-style propulsion or face extinction, renowned British cosmologist Stephen Hawking said today. Referring to complex theories and the speed of light, Hawking, the wheel-chair-bound Cambridge U physicist, told BBC radio that theoretical advances could revolutionize the velocity of space travel and make such colonies possible. "Sooner or later, disasters such as an planetisimal collision or a nuclear war could wipe us all out. But once we spread out into space and establish independent colonies, our future should be safe", said Hawking, who was due to receive the world's oldest award for scientific achievement, the Copley medal, from Britain's Royal Society. Previous winners include Albert Einstein and Charles Darwin.
. . In order to survive, humanity would have to venture off to other hospitable planets orbiting another star, but conventional chemical fuel rockets that took man to the moon on the Apollo mission would take 50,000 years to travel there, he said.
. . Hawking, a 64-year-old father of three who rarely gives interviews and who wrote the best-selling "A Brief History of Time", suggested propulsion like that used by the fictional starship Enterprise "to boldly go where no man has gone before" could help solve the problem. "Science fiction has developed the idea of warp drive, which takes you instantly to your destination", said. "Unfortunately, this would violate the scientific law which says that nothing can travel faster than light." However, by using "matter/antimatter annihilation", velocities just below the speed of light could be reached, making it possible to reach the next star in about six years. "It wouldn't seem so long for those on board", he said.
Nov 26, 06: An eruption of high-energy radiation recently signaled a tantrum unleashed by a black hole, astronomers announced. The event, which occurred near the crowded center of our galaxy, is a rare prize for astronomers.
. . Data came from the European Space Agency's orbiting gamma-ray observatory, Integral. Gamma rays are the highest form of radiation known. The Integral astronomers notified other observatories, and a watch began for the gamma rays, X-rays and other wavelengths of light.
. . As the doomed star orbits the black hole, it leaves its gas in what's called an accretion disk surrounding the black hole. Occasionally, this accretion disk becomes unstable and collapses onto the black hole, causing the kind of outburst Integral witnessed. Astronomers expect Integral to see such an outbursts only once every few years in our galaxy.
Nov 24, 06: Scientists turned on a massive telescope built on one of Mexico's tallest mountains today, hoping to get a glimpse of the beginning of the universe. With a base like a launching pad and an antenna the size of a big Ferris wheel, the Large Millimeter Telescope or LMT, will be used to pick up electromagnetic radiation known as millimeter waves emitted 13 billion years ago, when the first stars burst into existence, astrophysicists say.
. . The $128 million telescope is a U.S.-Mexican project built on the 4,580-meter summit of Sierra Negra, Mexico's fifth-highest peak, in air so thin that bottled oxygen is kept at hand in case workers faint. Sierra Negra, an extinct volcano to the east of the city of Puebla in central Mexico, was chosen because of its height and mild climate. While oblivious to light pollution, millimeter telescopes work best at altitudes where the level of water vapor in the air is low. With an antenna diameter of 50 meters, the LMT dwarfs existing millimeter-wave telescopes and should be able to pick up signals from the faintest objects.
. . While optical telescopes detect light rays and others look for radio, infrared or gamma waves, the LMT picks up electromagnetic radiation at wavelengths of 1 to 3 millimeters --shorter than radio waves but longer than infrared, visible light and gamma rays.
Nov 23, 06: Brown dwarfs are big balls of gas that can be up to 70 times as massive as Jupiter but not massive enough to carry out the thermonuclear fusion of hydrogen that powers real stars. Generally, the lower cutoff is thought to be at 13 times the mass of Jupiter, a level that triggers the fusion of deuterium, which gives brown dwarfs a warm glow that Jupiter can't muster.
. . As Geoff Marcy puts it: "Categorizing them does not magically add insight."
Nov 20, 06: X-ray vision has brought astronomers closer than ever to completely characterizing a black hole, a place where strange things happen. Astronomers measured the spinning speed of three black holes, finding that one rotates at a breakneck 950 times per second, nearing its theoretical rotation limit of 1,150 spins a second.
. . When any mass, such as a star, becomes more compact than a certain limit, its own ravity becomes so strong that the object collapses to a singular point, a black hole. The spin of a star is thought to translate into spin of a black hole that forms from the star's collapse. With its mass much more compact, the spin rate ought to be phenomenal, much like a skater pulls in his arms to increase speed when performing a pirouette.
. . While astronomers have calculated the masses of more than a dozen black holes, spin-speed measurements have remained elusive. Until now, the spin rate of only one other black hole has been accurately measured. The faster a black hole spins, the smaller its critical radius. That's because when a black hole is spinning, it drags space-time around with it. So if surrounding matter is spinning in the same direction as the black hole, it gets tugged along due to this so-called frame-dragging effect. "The space is being pulled, so it's helping the particle go around, so it's able to hang on much closer to the black hole", Narayan explained. "If a particle is going around a black hole in the same direction as the spin of the black hole, then it turns out that it can be comfortable. It's able to find a circular orbit even at much smaller radii", Narayan explained.
Nov 16, 06: New clues that cosmic rays, high-energy particles that travel space and bombard the Earth, are generated by shock waves in supernova remnants were revealed by a new study using NASA's Chandra X-ray observatory.
. . Cosmic rays are composed of high-energy electrons, protons and ions. Scientists used the Chandra observatory to study the X-rays emitted by the electrons (the only one of the particles that emits X-rays) from cosmic rays emanating from Cassiopeia A, a 325-year-old supernova remnant.
. . Scientists have long theorized that the high-energy shock waves of exploded stars called supernovas, were among "the few places in the galaxy that have enough energy to accelerate these particles." Stage says that it is likely that protons and ions would be accelerated in the same way as the electrons. "Explaining where cosmic rays come from helps us to understand other mysterious phenomena in the high-energy universe."
Nov 16, 06: Suns that exploded 9 billion years ago have helped prove that a mysterious force called dark energy was pushing the universe apart even back then, scientists reported.
. . They still do not understand dark energy --which appears to be everywhere, pushing everything apart with its repulsive power. But now they may be on the right track. And their findings, made with the help of the orbiting Hubble Telescope, suggest that Albert Einstein was right yet again when he predicted that an energy force, which he called the Cosmological Constant, permeated the universe.
. . This strengthens evidence suggesting the expansion of the early universe after the Big Bang first slowed but then began to accelerate around 4 to 5 billion years ago. The scientists came to this conclusion by studying 24 distant stars that exploded in blasts known as supernovae 9 billion years ago, when the universe was half the size it is now.
. . "Supernovae are cosmic mile markers." These particular supernovae are helpful because they all exploded at the same size --1.4 times the mass of our own sun. So by measuring their apparent brightness, astronomers can measure how far away they were and thus how fast the universe is expanding.
. . Although there are competing theories about what the universe is doing, the most accepted idea currently is that the universe is expanding at a rate that will allow it to continue expanding forever, as opposed to a "steady-state" universe or one that will eventually contract.
Nov 15, 06: Astronomers have spotted 20 new star systems in our local Solar neighborhood, adding to a rapidly growing list of known stellar residents in our galaxy.
. . The just-discovered stars reside within 33 light-years of Earth and include the 23rd and 24th closest stars to the Sun. The closest is a three-star system called Alpha Centauri located 4.36 light years from Earth. Within the past six years, astronomers' catalogue of nearby stars has ballooned by 16%.
. . The 20 newly reported objects are all red dwarf stars, which now account for 69% of the Milky Way's residents. Finding these relatively dim stars has not been easy. "Red dwarfs are among the faintest but most populous objects in the Milky Way", said team leader Todd Henry of Georgia State U. 'Although you can't see a single one with the naked eye, there are swarms of them throughout the galaxy.'
. . They include a binary red dwarf setup called SCR 0630-7643 AB, located 28.7 light years from Earth. The two stars orbit each other every 50 years or so and are within 7.9 astronomical units (AU) of each other, a bit less than the distance between the Sun and Saturn.
Nov 14, 06: The first satellite dedicated solely to seeking out new planets beyond the Solar system will go up December 21. the European Space Agency (ESA) said. The French project, dubbed COROT, will send into orbit a telescope capable of detecting smaller planets than is currently possible --some maybe just a few times the size of Earth and rocky, rather than the larger, gaseous types, ESA said.
. . "COROT could detect so many planets of this new type, together with plenty of the old type, that astronomers will be able to make statistical studies of them."
. . It will be able to detect smaller, rocky planets by using a different method. It will measure the light emitted by a star and detect the drop in brightness caused when a planet passes in front it. Like the larger planets found so far, however, these new ones will have to be orbiting close to their star.
. . In 2008, NASA is due to launch the first space telescope capable of detecting Earth-sized planets in similar orbits to ours.
Nov 7, 06: Nasa's Swift satellite has seen a giant flare explode from a nearby star. Sol also flares when twisted magnetic field lines in the solar atmosphere suddenly snap --but this was on a far bigger scale, scientists say.
. . The energy released by the II Pegasi star was equivalent to about 50 million trillion atomic bombs, they calculate. If Sol was ever to produce such an outburst, it would blast the Earth with radiation and almost certainly cause a mass extinction.
. . Fortunately, there is no trace in the geologic record that Sol has ever let go in this fashion, and Earth's magnetic field does a robust job of deflecting most of the high-energy particles and radiation our star will hurl at the planet in a normal flare.
. . II Pegasi is a two-star, or binary, system that is 135 million light-years from Earth, & is 0.8 times the mass of the Sun; its companion is 0.4 solar masses. The stars are close, only a few stellar radii apart. As a result, tidal forces cause both stars to spin quickly, rotating in step once in seven days compared to Sol's 28-day rotation period. Fast rotation is thought to be conducive to strong stellar flares.
Nov 6, 06: For years, astrophysicists have tried to reconcile a cosmic discrepancy: the universe held much less helium-3 gas than was predicted by models of stellar evolution. But by using new 3-dimensional models, scientists think they've discovered where all the helium 3 went --it was destroyed by the very stars that were thought to eject it into space, according to a new study.
. . Just after the Big Bang, the gases that made up the universe were predominately hydrogen, with 10% helium-4 and just .001% helium 3. According to previous models of stellar evolution, low mass stars (about 1 to 2 times the size of our Sun) should have produced large amounts of helium-3 and increased its percentage in the universe to .01. But observations showed that the amount of helium 3 in the universe still at .001%.
. . In what he described as a case of serendipity, he and his colleagues found the answer of the missing helium 3 while they were modeling a "near explosion" called a helium flash, which occurs when a star switches from burning hydrogen to burning helium.
. . Stars like Sol burn hydrogen at their cores for nearly 10 billion years. As the star ages, it exhausts all the hydrogen at its core to become a red giant and begins to burn helium. The star also loses much of its mass through stellar winds. The expelled material was thought to be rich in helium-3. (Heavier elements like carbon, nitrogen, and oxygen have accumulated in the universe through this same mechanism.)
. . While modeling the helium flash, Eggleton and his colleagues found an unexpected instability elsewhere in the star that "seemed to explain two phenomena that had been a bother for several years." The instability mixed helium 3 in the outer layers of the star into deeper layers where it was hot enough for it to be burned up, solving the problem.
. . The instability also explained why older stars were observed to have increasing abundances of carbon-13 and nitrogen-14 when they weren't expected to. Like the helium-3, carbon-12 and nitrogen-13 located nearer the surface were also mixed deeper into the star where they were converted into carbon-13 and nitrogen-14 respectively.
Oct 30, 06: The stellar residents of the jam-packed celestial cities known as globular clusters employ a traffic system that causes lightweight stars to zoom to the city edges while keeping giants centrally located, astronomers have concluded. The study gives the first direct evidence of such sorting, called "mass segregation", a process long suspected to occur in globular clusters but never observed.
. . A globular cluster is a dense collection of 10,000 to more than a million stars in a region spanning just 10 to 30 light-years. The nearest star to our Sun, for comparison, is more than 4 light-years away.
. . The crowded conditions have made it difficult for astronomers to pinpoint with any accuracy individual stars, let alone their velocities. By placing a "picture frame" around the same cluster regions in a time sequence, they could track the positions of as many as 130,000 stars in each revealing the motions of the stars across the sky.
. . The method provided accurate speeds for almost 15,000 stars at the cluster's center, including 23 unusually hot and bright stars called blue stragglers thought to be the product of stellar collisions. The blue stragglers, which boast twice the mass of the average star, moved more slowly than typical stars, a finding that agrees with predictions for mass segregation.
Oct 25, 06: Harvard University astrophysicists Abraham Loeb and Matias Zaldarriaga suggest that tell-tale spikes in the energy spectrum which are made by TV and radio broadcasts could be discernible to telescopes such as the Low-Frequency Array (LOFAR) now being built in the Netherlands.
. . These spikes, if they are ever picked up, could be used to unlock key information from any alien world. TV and radio broadcasts are in the 50-400 megahertz range, which overlaps with the frequency range of between tens and hundreds of megahertz made by radio waves from hydrogen atoms forged in the early Universe.
. . As a planet orbits a star, its distance from Earth changes, which would cause a Doppler shift, or widening, in the frequency range of ET's emissions. Loeb and Zaldarriaga believe this shift will make it possible to deduce the shape of the orbit, the planet's tilt and distance from the star --which in turn will enable scientists to make a stab at calculating the planet's surface temperature and whether it could have liquid water.
. . As many as 100 million stars with planets lie within a sphere of 1,000 light years from Earth from which such radio leakage is possible, they calculate.
Oct 24, 06: The Sun had sisters when it was born, according to new research, hundreds to thousands of them. And at least one was a supernova, providing further support for the idea that there could be lots of planets around other stars since our solar system emerged in such an explosive environment.
. . "We know that the majority of stars in our galaxy were born in star clusters", said Leslie Looney, who arrived at the solar sibling finding. "Now we also know that the newborn solar system not only arose in such a cluster, but also survived the impact of an exploding star. This suggests that planetary systems are impressively rugged and may be common in even the most tumultuous stellar nurseries."
. . When massive stars explode and go supernova, they create radioactive isotopes that are blown outward and mix with nebular gas and dust as they condense into stars and planets. The evidence for the solar sisters was found in daughters --such as decayed particles from radioactive isotopes of iron-- trapped in meteorites, which can be studied as fossil remnants of the early solar system. These daughter species allowed Looney and his colleagues to discern that a supernova with the mass of about 20 suns exploded relatively near the early Sun when it formed 4.6 billion years ago; and where there are supernovas or any massive star, you also see hundreds to thousands of sun-like stars, he said.
. . The cluster of thousands of stars dispersed billions of years ago due to a lack of gravitational pull, Looney said, leaving the sisters "lost in space" and our Sun looking like an only child ever since, he said.
. . They calculate that the supernova sibling was about 0.32 to 5.22 light-years from the Sun at that time. The closest star system to Sol today is Alpha Centauri at 4.36 light-years. "The supernova was stunningly close", said Looney's co-author Brian Fields. "Our solar system was still in the process of forming when the supernova occurred."
Oct 19, 06: New images of the Andromeda Galaxy were captured by an infrared camera aboard the Spitzer Space Telescope. "We thought it was a plain, ordinary galaxy with two companions around it. But now we understand its structure. It will be used as a computer model to understand and study the early universe", Fazio said.
. . The cosmic crash is believed to have happened 210 million years ago when dinosaurs roamed the earth, but is a relatively recent occurrence in the grander scheme of time, scientists said.
. . After the images from the telescope were entered into a computer model, it revealed how a small galaxy hit the center, or "sweet spot", of its larger neighbor with such force it fired off new stars, space dust and two rings of fire.
Oct 19, 06: Our giant neighboring galaxy, Andromeda, was involved in a head on collision with the dwarf galaxy, M32, some 210 million years ago, scientists announced.
. . Infrared images from NASA's Spitzer Space Telescope recently revealed a never seen before ring of dust within Andromeda. The new ring and the presence of a previously observed outer ring suggest a disturbance that could have only been caused by a collision. Astronomers suspect that the impact was brought about by the dwarf galaxy Messier 32 (M32).
. . To recreate the impacts of the crash, the researchers used computer models. The simulations showed that M32 plunged through the disk of Andromeda along Andromeda's polar axis back when dinosaurs roamed the Earth. In the crash, M32 lost more than half of its original mass and the much more massive Andromeda was disrupted.
. . Astronomers say that Andromeda --currently 2 million light years away from the Milky Way-- will collide with our galaxy in 5 billion to 10 billion years. The two will eventually join to form one large elliptical galaxy.
Oct 17, 06: A seemingly violent collision of two galaxies is in fact a fertile marriage that has birthed billions of new stars, and an image released on Tuesday gives astronomers their best view yet.
. . The new image of the Antennae galaxies allows astronomers working with the orbiting Hubble Space Telescope to distinguish between new stars and the star clusters that form them. Most of these clusters, created in the collision of the two galaxies, will disperse within 10 million years but about 100 of the largest will grow into "globular clusters" --large groups of stars found in many galaxies, including our own Milky Way.
. . The Antennae galaxies, 68 million light years from Earth, began to fuse 500 million years ago. The image serves as a preview for the Milky Way's likely collision with the nearby Andromeda Galaxy, about 6 billion years from now.
Oct 12, 06: Spitzer's measurements suggested atmospheric gases were instead absorbing and re-radiating sunlight rapidly. The finding represents the first time that any kind of variation has been seen across the surface of an extrasolar planet (also sometimes called exoplanet). It is what is known as a "hot-Jupiter" planet, because it is made of gas like our Jovian giant, and is hot, due to its tight, 4.6-day-long journey around its star.
Oct 12, 06: Fire or ice --astronomers have discovered that a distant planet is both. With one side always hot as lava and the other chilled possibly below freezing, Upsilon Andromeda b is a giant gas planet that orbits extremely close to Upsilon Andromeda, a star 40 light-years from the Solar System.
. . It's also probable that the planet is tidally locked to its star the way Luna is with Earth, so that one side of the planet always faces --and is always heated by-- its star. The gas giant circles its star in a very tight orbit --4.6 days. Two other planets also circle Upsilon Andromeda, but farther out.
. . The new finding, detailed online in the journal Science, marks the first time any kind of temperature variation has been seen across the surface of a planet outside our solar system. Using infrared data collected by NASA's Spitzer Space Telescope, the researchers calculated that temperatures on the sunlit side of the Upsilon Andromeda b were between 1,400 to 1,650 degrees C but only 20 to 230 degrees C on the dark side. Jupiter, in contrast, maintains an even temperature all around. The findings likely apply to other hot-Jupiters as well, the researchers say.
Oct 10, 06: The closest planet outside the Solar System orbits a young Sol-like star only 10.5 light years away --so close that telescopes might soon be able to snap pictures of it, new observations confirm. About 1.5 more massive than Jupiter, the planet takes 7 years to circle its star, Epsilon Eridani.
. . Astronomers think enough starlight might be reflected off the planet when it makes its nearest approach to Epsilon Eridani in 2007 for Hubble and other telescopes to image it.
. . If moons circle the planet, they might have temperatures similar to Earth's and possibly liquid water, said study team-member. [And closer to Earth's *size, too! That's more interesting, isn't it? Ya can't land on --or colonize-- a huge gas-giant.] However, the planet's orbit takes it so far from its star that any oceans on the moons would then freeze. Still, life could potentially survive on such moons if they were massive enough to retain a dense heat-trapping atmosphere like Saturn's moon, Titan.
. . A second planet with a longer orbit might also circle Epsilon Eridani, but this has yet to be confirmed.
Oct 10, 06: Instead of being perfectly round like a globe, the universe might be a bit stretched in shape like a pill. The newly proposed shape could be caused by a magnetic field that pervades the entire cosmos or defects in the fabric of space and time, researchers said.
. . Scientists in Italy base their proposal off data gathered by a NASA satellite known as the Wilkinson Microwave Anisotropy Probe (WMAP).
. . So far, data from this probe has helped nail down some of the most important details about the universe. This includes the age of the universe since the Big Bang, at 13.7 billion years; the time when the first atoms formed, at 380,000 years after the Big Bang; and how much of the universe is made of either ordinary matter or the mysteries known as dark matter and dark energy, at roughly 5, 25 and 70%, respectively.
. . The universe may be roughly 1% more eccentric, or nonspherical, than previously often believed. An ellipsoid universe could be caused by a magnetic field pervading the cosmos that stretches space-time, he said, or by space-time defects such as cosmic strings, immensely dense structures just a proton or so wide stretched to intergalactic scales, whose gravity could distort space and time. The data weakly favor the ellipsoidal model.
Oct 5, 06: A new census compiled by astronomers contains the location of every local galaxy with a supermassive black hole at its center.
June 06, 06: The textbook account of where planetary systems come from --namely, disks of dust and gas that encircle stars-- may require an addendum. Researchers have found that comparable disks girdle distant exoplanets far less massive than our sun. The discovery raises the possibility that these planetary mass objects, or planemos, are orbited by other planets and moons-- like the Solar system, but smaller.
. . The smallest of the planemos is still five times the size of Jupiter. Jupiter's largest moons probably arose from one of these disks, sez Jayawardhana.
Oct 4, 06: Astronomers have discovered a possible new class of planets outside the Solar System that hug their parent stars tightly. Working with the Hubble Telescope, they've so far identified five to 16 possible planets that orbit their parent stars in as few as 10 hours... up to 3.2 days. They found the planets in a faint, crowded star field in a region of the Milky Way known as the Galactic bulge.
. . These worlds generally orbit stars that are somewhat lighter than the typical stars where extrasolar planets have been found before. Any planets which orbited at such a close distance to brighter, hotter stars would be destroyed by solar radiation.
Sept 28, 06: Australia or South Africa will get to host one of the great scientific projects of the 21st Century. The countries have been shortlisted to be the home of the 1bn-euro-plus Square Kilometer Array (SKA), a giant next-generation radio telescope. The SKA's huge fields of antennas will sweep the sky for answers to the major outstanding questions in astronomy. They will probe the early Universe, test Einstein's theory of gravity and even search for alien intelligent life. The steering committee tasked with pushing the project forward has now settled on the two prime locations where the exacting technical demands of the telescope could be met. The project aims to produce a radio telescope with a collecting area of one million square meters --equivalent to about 200 football fields.
. . Outrigger facilities, which will be many hundreds, even thousands, of km away will then send their data to be combined with those of the central station. This practice known as interferometry is widely used by astronomers today.
. . "The 'holy grail' in this game would be to find pulsars going around a black hole. When we find that, we can do tests on gravity that go way beyond what is possible at the moment --and many people believe Einstein's theory will fail those tests."
. . "Our television systems and our airport radars transmit at the sorts of frequencies that the SKA will be sensitive to. If there are other technological civilisations out there within a few hundred light-years, we would detect the leakage radiation from their planets."
. . The first elements of the SKA should come online in 2014, with the full network of antennas in operation by 2020.
Sept 26, 06: Skywatchers witnessed the spectacular explosion of a dying star. That was the year 185 AD. Today astronomers said they might have identified the remains from this ancient stellar explosion, now considered the oldest supernova on record.
. . Chinese astronomers noted the bright light in the sky twinkled like a star but didn't appear to move, arguing against the object being a comet. Within eight months, they recorded, the bright light faded, a phenomenon that astronomers now know is consistent with supernovas.
. . "I think it is very interesting that we can now say with some confidence, but not absolute certainty, that RCW 86 is the remnant of AD 185", said Jacco Vink of the University of Utrecht.
. . RCW 86 is encased in an expanding shock wave formed during its transit from the original explosion. By peering into one part of RCW 86, the astronomers calculated how fast this cosmic bubble was moving. So with the size and speed of RCW 86, the astronomers could calculate the time of the explosion, and hence the remnant's age. "Our new calculations tell us the remnant is about 2,000 years old."
Sept 26, 06: A new wide-field survey of the sky has made its first major discovery --two planets orbiting far-distant stars. The SuperWasp project uses camera lenses and super-sensitive detectors to monitor stars for tiny dips in light that might betray a passing planet.
. . The 2 are what astronomers term "hot Jupiters". Jupiter is almost 700 million km from the Sun and takes some 12 years to complete an orbit, these planets are just a few million km from their stars and take only a couple of days to complete an orbit. Scientists think that of the 200 or so extrasolar planets detected to date, these may be among the hottest of the lot. Wasp-1b's temperature is estimated to be over 1,800C (3,300F).
. . Night after night, the SuperWasp robots watch millions of stars for small deviations in brightness that might be the result of an orbiting planet passing across the stellar disc. With just one narrow-field telescope, the chances of seeing such transits would be very small; but the odds rise dramatically for SuperWasp because its automated systems can filter a huge sample of stars.
. . SuperWasp's goal is to find the planets that more specialist telescopic systems can then investigate more closely. Once a target has been confirmed, astronomers can book time on the likes of the Hubble and Spitzer space observatories to examine the object at infrared wavelengths. "This tells us quite a lot about the weather on them."
. . "All the theoretical models tell us that these planets should have dense cloud decks made essentially of 'rock snowflakes'; the sorts of chemicals which condense to form clouds at these high temperatures are things that we normally think of on Earth as minerals - olivine, forsterite, all the magnesium silicates." Professor Collier Cameron said astronomers wanted to try to find out how such weather systems transported intense heat around a planet.
. . Later this year, French scientists will launch the Corot mission. This space telescope will also look for transiting events, but it will see deeper into the sky than SuperWasp and detect lower-mass planets, ones that are perhaps just a little bigger than Earth.
Sept 25, 06: A sizzling-hot star is spinning around at near break-up velocity, according to a new study. It's about 300 light-years from Earth. Alpha Arae is the nearest "Be star"--a class of rapidly rotating stars that are very luminous, massive and hotter than Sol.
. . Astronomers wonder if material will be ejected from the star, called Alpha Arae. Matter may freely escape the equatorial regions, 'launched' by the centrifugal force. At its equator, the star is spinning at 470 kilometers per second--ear its break-up velocity-- and speedy enough to supply the needed angular momentum to the disk.
. . The high spin rate at the equator may cause material to be ejected from the star and into a swirling disk. "Such dense disks generally only appear around stars that are forming from a region that is already a high density gas, so they draw from their environment to form disks. But Be stars have cleared out their environment so it is expected that the disk must come from the star itself.
Sept 21, 06: Recent images from the depths of cosmos show more than 500 galaxies in the early universe, scientists reported today. The galaxies --viewed with the Hubble Space Telescope-- existed less than a billion years after the Big Bang, the purported birth of our universe, and flourished when the cosmos was less than 7% of its current age. They are smaller than most of today's giant galaxies and sport a blue shade, a signature of blazing star births. The blue light, which took almost 13 billion years to arrive on Earth, was shifted to a red color because the expansion of space stretches the wavelength of light. This redshift helps astronomers figure out when the light was emitted.
. . "Finding so many of these dwarf galaxies, but so few bright ones, is evidence for galaxies building up from small pieces-merging together as predicted by the hierarchical theory of galaxy formation," said study leader Rychard Bouwens, an astronomer at the University of California.
Sept 20, 06: Astronomers have discovered a distant supernova, or exploded star, so large that it will force scientists to question their understanding of how certain older stars disintegrate.
. . Scientists have believed that dying stars known as "white dwarfs" can't expand to more than 1.4 times the size of our sun without exploding in a massive thermonuclear blast. That rule, known as the "Chandrasekhar Limit", has served as the foundation of decades of astrophysical research and helped scientists estimate the size of the universe.
. . But a team of astronomers said today that they have found a supernova in a galaxy 4 billion light years away that reached a mass twice that of the sun before exploding. The star could have been spinning so fast that centrifugal force pushed it beyond the usual limit, Howell and other researchers said. The explosion also could have come from two white-dwarf stars merging.
. . White dwarfs typically explode into supernovas after pulling gases from a nearby star. Because they give off a consistent light, these supernovas can serve as markers that help measure the universe. Scientists relied on them to discover in 1998 that the universe is expanding at an accelerating rate.
. . The new supernova doesn't necessarily undermine that discovery or other previous research, the astronomers said. But scientists should be more cautious about incorporating the Chandrasekhar Limit into their future work.
Sept 19, 06: Some scientists theorize that small, solid planets outnumber gas giants (10:1 is a conservative estimate).
Sept 18, 06: Discovered just 11 years ago, a class of oddball "failed stars" continues to baffle as well as enlighten astronomers. Now researchers have spotted for the first time one of these failed stars, called a brown dwarf, with a companion planet-both orbiting a Sun-like star.
. . It is 50 times the mass of Jupiter and thus considered a T brown dwarf --the coolest of the two brown-dwarf categories. This slow smoldering releases infrared light, which was detected by NASA's Spitzer Space Telescope.
. . One reason the dwarf stayed out of view until now, Lunham said, is its lengthy distance from its planet partner, which the researchers spotted using the Doppler method. This technique measures the wobbles of a star caused by the gravitational tug of an orbiting object that otherwise can't be detected.
. . However, the method is limited: Whereas the planet orbits at a snug 0.3 astronomical units (AU) from the Sun-like star called HD 3651, the brown dwarf resides at a distance of 500 AU.
. . Due to the brown dwarf's prolonged orbit time of more than a thousand years, and its miniscule gravitational effect on the star, Doppler was unable to pick up the object.
. . The discovery helps to clear up a quandary. When astronomers discovered the system's Saturn-sized planet in 2003, they didn't know the cause of its elongated, elliptical orbit. Now they suspect the tug from the brown dwarf's gravity could be partly responsible for stretching the planet's orbit.
Sept 18, 06: The Milky Way might not have formed through the merger of several smaller galaxies as previously thought, but by some other unknown process, a new study suggests. Until now, the best theoretical models predicted dwarf galaxies beget larger and larger galaxies, as multiple star packs clumped together or a heftier galaxy started gobbling up its neighbors. If this were the case for the Milky Way, Zoccali said, the stars in the galactic bulge should have once been part of the disk. Over eons, as more galactic mergers occurred, some of the stars should be tugged toward the center to form the bulge.
. . "We have proved that this is not the case", Zoccali said. Using the European Southern Observatory's Very Large Telescope (VLT) array in Paranal, Chile, an international team of astronomers, led by Zoccali, examined the chemical makeup of 50 giant stars in the direction of the galactic bulge. They discovered the stars at the center of the Milky Way showed distinct element amounts compared to the disk stars, a sign that the two galaxy components formed separately. "In other words, bulge stars did not originate in the disk and then migrate inward to build up the bulge but rather formed independently of the disk."
Sept 14, 06: Scientists said today that they have discovered an unusually large and light planet orbiting a star that could force them to reexamine theories about how planets are formed. The planet, dubbed HAT-P-1, is roughly one-third larger than Jupiter but only weighs half as much --about one-quarter the density of water.
. . Itrevolves around its parent star once every 4.5 days in an orbit one-seventh of the distance from Mercury to the Sun --one-twentieth of the distance that separates Earth from our own star.
. . Its parent star, one of a double-star system, is about 450 light-years from Earth --too faint to see with the naked eye but can be spied with binoculars.
. . Scientists detected the planet because light from its parent star dims when the planet passes in front of it. The large size could be the result of heat coming from the interior of the planet, though they have yet to determine how that could happen.
Sept 13, 06: Scientists said today that they have found the most distant galaxy yet, nearly 13 billion light-years away, in a discovery that could help explain how stars were formed at the dawn of time. The galaxy, named IOK-1, is so far away that the light waves that reached Earth depict it as the system of stars existed shortly after the Big Bang created the universe 13.66 billion years ago.
. . They found only one object that could be identified as a galaxy, leading them to believe they were witnessing a process known as reionization, when the first stars cooked free-floating hydrogen atoms into the transparent plasma gas that fills much of the universe today. According to this theory, light from other galaxies as old as IOK-1 is blocked by hydrogen atoms that were still whole and had not yet gone through reionization.
. . Another theory holds that few galaxies existed during this time, 780 million years after the Big Bang. It would mean that reionization had already taken place.
. . From other observations, astronomers expect to see these first stars somewhere between a redshift of 8.6 and 13.6. This is between 570 and 300 million years after the Big Bang.
. . Dr McMahon himself hopes to get out to 7.7 and 8.7 with a new instrument called Dazle (Dark Age Redshift Lyman Explore). It will be fitted to the Very Large Telescope in Chile next month.
. . A refurbished Hubble telescope --if the US space agency gives the go-ahead for a final servicing mission-- should be able to reach up to redshift 10. Its successor, the James Webb Telescope, due for launch early in the next decade, is expected to get to redshift 15.
Sept 13, 06: Through computer simulations, scientists examined the formation and evolution of giant planet systems recently detected outside the Earth's solar system. Their results revealed that more than a third of them might contain planets that could potentially support life and could even be covered with deep oceans.
. . Hot Jupiters shift around the rotating disks of dense gas surrounding a newly formed star and fling rocky debris outward where they could merge to form planets like Earth. At the same time, small icy bodies in the outer reaches of the disk are slowed down and pulled in towards the planets by the violent forces from the surrounding gas. These icy formations deliver water to the planets, which can then host huge oceans, the thinking goes.
. . Scientists had previously thought that as hot Jupiters plowed through the dense gaseous material on their inward migrations toward parent stars, all the surrounding material would be either "vacuumed up" or ejected from the system, Raymondsaid. "The new models indicate these early ideas were probably wrong."
Sept 7, 06: The Hubble Space Telescope has spied one of the smallest objects ever detected around a normal star. The object further blurs the line between stars and planets and raises new questions about how planets should be defined outside our solar system.
. . The newly spotted object is a companion to CHXR 73, a low-mass red dwarf star. With 12 times the mass of Jupiter, CHXR 73 B straddles the line between the largest planets and the smallest stars. The latter are called brown dwarfs.
. . CHXR 73 B is located about 19.5 billion miles (31.3 billion km) from its parent star, or roughly 200 times farther than Earth is from our Sun. This distance is so great that even though CHXR 73 B has about the right mass to be a planet, it likely didn't form in the same way that planets in our solar system did
. . According to standard planet formation theories, planets are created from the disks of gas and dust surrounding newborn stars. But the circumstellar disks of red dwarf stars are typically no more than 10 billion miles (16 billion km) in diameter. Furthermore, theory predicts that gas-giant planets like Jupiter should form no more than about 4.8 billion km from their stars. CHXR 73 B is located far beyond both these limits.
. . More likely, scientists say, CHXR 73 B formed in the manner of stars: from the gravitational collapse of large, diffuse clouds of hydrogen gas. For this reason, Luhman believes CHXR 73 B should be regarded as a brown dwarf. Luhman believes an extrasolar object's formation history is more important than mass when determining whether it is a planet or not.
. . In a twist that surprised many astronomers, the definition of planet recently adopted by the IAU is not meant to apply to objects around other stars. Also, it does not take formation history into account.
Sept 7, 06: Earthlike planets covered with deep oceans that could harbor life may be found in as many as a third of Solar-type systems discovered outside of our own, U.S. researchers said.
. . These Solar-type systems feature gas giants known as "Hot Jupiters", which orbit extremely close to their parent stars --even closer than Mercury to Sol. The close-orbiting gassy planets may help encourage the formations of smaller, rocky, Earthlike planets. "We now think there is a new class of ocean-covered, and possibly habitable, planets in solar systems unlike our own."
. . The gas giants may help rocky planets form close to the suns, and may help pull in icy bodies that deliver water to the young planets, they found. "I think there are definitely habitable planets out there", Raymond said. "But any life on these planets could be very different from ours. There are a lot of evolutionary steps in between the formation of such planets in other systems and the presence of life forms looking back at us."
. . As many as 40% of the 200 or so known planets around other stars are Hot Jupiters, the researchers said.
Sept 8, 06: A planet slightly larger than Jupiter was recently spotted as it passed in front of a Sol-like star 500-light-years away. Called TrES-2, the new extrasolar planet is the second to be discovered using telescopes built from off-the-shelf components similar to those used by amateur stargazers. All 3 were small 10-cm (4-inch) telescopes built using a combination of off-the-shelf parts and custom-made lenses.
. . TrES-2's close proximity to its star means it takes only about 2.5 days to make one orbit. Jupiter, in contrast, takes nearly 12 years.
. . Currently, some 200 extrasolar planets are known; eight of them were discovered using the transit technique.
Sept 5, 06: Supermassive black holes play a stealthy role in two major types of galaxies in the universe, bulking up until they are big enough to effectively shut down the formation of new stars, scientists have found.
. . The new results explain why scientists have observed in the past that massive galaxies have fewer young stars. Black holes, monstrous heaps of dense matter, grow at a different rate than the galaxies that surround them. But once a black holes reach a critical mass and become too large for its host galaxy, it zaps away nearly all the gas needed for young stars to form.
. . Black holes are "messy eaters", Khochfar said. As matter falls towards a black hole, momentum forces it to flatten out into a dense, hot disk. A lot of the matter never makes it into the black hole and is ejected in jets that travel at a significant fraction of light-speed, emanating from the poles of the black hole. Those jets might do such a good job of heating gas near the center of a galaxy that there is little fuel available for the creation of new stars.
Aug 30, 06: Teams of international scientists have used observations from NASA's Swift satellite and other telescopes to witness the evolution of a cosmic blast into a stellar explosion or supernova. The blast is thought to be a milder type of gamma-ray burst (GRB) --the most powerful type of explosion known to astronomers-- called an X-ray flash. X-ray flashes appear to signal an explosion that leaves behind a neutron star while gamma-ray bursts are thought to mark the birth of a black hole, a region of space from which nothing can escape.
. . It is known as GRB060218 after the February 18 date it began, about 440 million light years away. It is the second-closest gamma-ray burst ever detected and the first view of a supernova in the act of exploding. The star had a smaller mass than those estimated for the normal GRB-supernova.
Astronomers had to climb atop platforms on the sides of the giant instruments and constantly monitor the night sky to keep in focus those stars whose light were being slowly collected onto photographic plates. A telescope's speed had to be continually adjusted by tapping buttons on a control paddle, and on the morning after a cold night, an astronomer might find that his tears had frozen him to the eyepiece.
. . But those days are long gone. Automated telescopes are now doing work once done by tortured astronomers, and thanks to a new high speed wireless microwave network, today's digitally captured images can be beamed down from mountain observatories and quickly distributed to astronomers living thousands of miles away.
. . Called the High Performance Wireless Research and Education Network, or HPWREN for short, it can transfer data at 45 megabits-per-second, or about 30 times faster than today's fastest DSL connections.
Aug 21, 06: New observations of a great big cosmic collision provide the best evidence yet that invisible and mysterious dark matter really does exist. The collision, between two huge clusters of galaxies, is the "most energetic cosmic event, besides the Big Bang, that we know about", said Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics.
. . The impact split normal matter and dark matter apart, rendering the dark matter's gravitational presence observable.
. . Given what's known, this is the makeup of the universe:
. . * 5% normal matter
. . * 25% dark matter
. . * 70% dark energy
Dark energy is an even more mysterious phenomenon, a force of some sort that beats out gravity and is causing the universe to expand at an ever-faster pace.
. . Some theorists have suggested that rather than invoking dark matter, perhaps existing ideas about gravity might be wrong. Maybe gravity is stronger on intergalactic scales than what is predicted by Newton and Einstein.
. . And all astronomers agree that dark matter is such an exotic idea as to border on the crazy. "A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking", said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists."
. . The image reveals: The hot gas-normal matter-was slowed by a drag force described as the cosmic equivalent of air resistance. But the dark matter was not slowed by this effect, presumably because it does not interact with normal matter, as theory had predicted. So the normal matter and dark matter became separated.
. . "No matter what you do [in devising new theories] you're going to have to believe in dark matter. We've closed this loophole about gravity, and we've come closer than ever to seeing this invisible matter", Clowe said. "This is the first time we've had a direct detection of dark matter" in which you can't explain the results with any altered-gravity theory, he said.
Aug 17, 06: Researchers peering at the Universe's first-born stars have uncovered the key to predicting a star's destiny.
. . Stars that don't have enough mass never shine, dying billions of years before their bigger counterparts. But astronomers have never been able to measure the exact mass limit, because the lightest stars that do shine can be simply too faint to detect.
. . Now, new images show for the first time how big a star must be to avoid impending doom. Astronomers have viewed high quality pictures of some of the faintest stars in our galaxy for the first time. The images come from the dimmest members of the NGC 6397 cluster --ancient stars that orbit the Milky Way's center in a close-knit group.
. . "The light from these faint stars is so dim that it is equivalent to that produced by a birthday candle on the Moon, as seen from Earth." The Hubble Space telescope's advanced camera was focused on the stars for five days to detect the tiny pinpricks of light. Although the telescope would have been able to detect fainter stars, none could be found --so it appears that they simply don't exist.
. . Almost everything about a star's fate is determined by the mass of the gas cloud from which it is formed. Gravity pulls the gas into a giant ball, or protostar. As the ball gets bigger and more solid, its center becomes extremely hot. For large protostars, the heat becomes so intense that the star begins to burn hydrogen by fusion, and so starts to shine. These stars can sustain themselves for billions of years, because their heat is self-replenishing. Some could live longer than the estimated lifespan of our Universe - in effect, forever.
. . Small protostars never make it this far. Their cores are just not hot enough for hydrogen fusion, so they never light up. They quickly stop shrinking and fade into brown dwarfs, or giant planets. A small difference in mass can therefore mean the difference between effective immortality and an untimely death.
. . How big is big enough? The problem has been that those stars that do start to shine - but have only just enough mass --burn very faintly and are nearly impossible to see.
. . The long-awaited new images finally lay this question to rest, say the authors. The dimmest stars were measured as being 8.3% of the Sun's mass. All protostars that are smaller than this are headed for life as a brown dwarf.
. . The pictures also provide a spectacular new record of the end of a star's life. Large stars, which burn out more quickly, can become white dwarfs- glowing cinders which slowly fade with age. Astronomers had predicted that these should turn blue as they move towards death. The new findings provide the first images of this signature color change, confirming expectations.
. . These ancient white dwarfs, which have never been seen before, are amongst the Universe's oldest stars. Now that astronomers can work out how long they have lived, they can refine estimates of the age of the Universe.
Aug 16, 06: A fundamental force that holds electrons inside atoms and governs how charged particles and light interact is a little weaker than previously thought, scientists reported.
. . The strength of electromagnetic force, one of the four fundamental forces of nature, is specified through a value known as the fine structure constant.? Through studying an individual electron in isolation, scientists were able to calculate a new value for this number that is six times more precise than previous estimates.
. . "Little did we know that the binding energies of all the atoms in the universe were smaller by a millionth of a percent --a lot of energy given the huge number of atoms in the universe", said Gerald Gabrielse, a researcher at Harvard.
. . Gabrielse and his colleagues developed a giant atom by isolating an electron in a bottle devoid of almost all particles and chilled to temperatures colder than the surface of Pluto. Similar to a real atom, they kept the lone electron in circular motion through electric and magnetic forces. The electron also wobbled down in the direction of the magnetic field, a setup similar to a merry-go-round, with an electromagnetic trap as the carousel and the electron as the lone horse.
Aug 14, 06: A heavy form of hydrogen created just moments after the Big Bang has been found in larger quantities than expected in the Milky Way, a finding that could radically alter theories about star and galaxy formation, researchers said. They used NASA's Far Ultraviolet Spectroscopic Explorer, or FUSE, satellite.
. . This form of hydrogen, called deuterium, has apparently been hiding out in interstellar dust grains, changing from an easily detectable gaseous form to a harder-to-see solid form.
. . Deuterium --a form of hydrogen with not only a proton but also a neutron in its nucleus-- produces a telltale spectral fingerprint in the ultraviolet light range, which FUSE can see.
. . So something in the theory is wrong, Linsky said. "This implies that either significantly less material has been converted to helium and heavier elements in stars or that much more primordial gas has rained down onto the galaxy over its lifetime than had been thought", he said. "In either case, our models of the chemical evolution of the Milky Way will have to be revised significantly to explain this important new result."
Aug 14, 06: For a star to form, gravity has to overcome buoyant magnetic forces that fight to keep a cloud of gas and dust from collapsing. Theorists have long suspected that the competition between gravity pulling inward and magnetic pressure pushing outward would produce a warped, hourglass pattern to the magnetic field within these collapsed cores.
. . Now they've finally found just such a shape. The setup is part of the Perseus molecular cloud complex, a vast collection of gas and dust holding as much mass as 130,000 suns where stars are actively forming.
. . The researchers observed dust emission from the cloud. Because the magnetic field aligns the dust grains in the cloud core, the team was able to measure the magnetic field's geometry and estimate its strength by measuring the polarization of the dust emission.
. . "With the special polarization capabilities of the SMA we see the shape of the field directly", said Ramprasad Rao (Institute of Astronomy and Astrophysics, Academia Sinica.) "This is the first textbook example of theoretically predicted magnetic structure."
Aug 9, 06: The case of the lithium that has gone missing since the Big Bang has been solved --the stars swallowed it, scientists said. The discrepancy between the quantity of lithium estimated to have been created at the start of the universe and the small amount now actually found has long perplexed astronomers, bringing into question fundamental planetary theory.
. . Scientific theory said that up to three times the amount of lithium --the lightest of the solid elements-- was produced along with the main elements hydrogen and helium in the Big Bang than can now be found in the older stars.
. . Whereas other elements were hurled back into the atmosphere by convection, lithium was dragged down into the star where it was destroyed [what?] when temperatures rose over 2 million degrees.
. . Based on observations of 18 stars of different ages, the team calculated that the original lithium content was 78% higher than that currently found --enough to account for the discrepancy with Big Bang estimates.
Aug 7, 06: Eight new complex, carbon-containing molecules have been found in two interstellar clouds. The team detected acetamide, cyclopropenone, propenal, propanal and ketenimine in Sagittarius B2 (N), while methyl-cyano-diacetylene, methyl-triacetylene and cyanoallene were found in the Taurus Molecular Cloud (TMC-1), the National Radio Astronomy Observatory announced.
. . The presence of complex, carbon-containing molecules in the Taurus Molecular Cloud, where temperatures reach only about 10 degrees above absolute zero, "has certainly changed the belief that large organic molecules would only have their origins in hot molecular cores."
Aug 7, 06: European astronomers are planning to build an optical telescope that is four times bigger than any in existence. With a main mirror around 42 meters wide, the Extremely Large Telescope (ELT) will allow remote objects to be studied in greater detail than ever before.
. . The powerful observatory will allow astronomers to see some of the first galaxies to form in the Universe. It could also look for signatures of life, such as vegetation, on distant planets circling other stars.
. . The European Southern Observatory (Eso) operates the 8.2m Very Large Telescope (VLT) at Cerro Paranal in Chile, which has been described as a "discovery machine". An average of 1.5 scientific papers published each day is based on observations carried out at the VLT.
. . The US is planning its own 30m telescope.
. . Eso had previously looked at the feasibility of building a telescope 100m in size --around the size of all the telescope mirrors in the world put together.
. . With a 100m telescope, astronomers may have been able to produce images of planets about the same size as Earth circling other stars. But this may be beyond the capabilities of a 42m telescope. However, it could allow scientists to study the atmospheres of so-called extrasolar planets, looking for the spectral signatures of life such as methane gas and chlorophyll.
. . Construction could begin as early as 2010-11. But there is still no agreement over where to site the project. Sites under discussion include South Africa, Tibet, Morocco, Greenland and Antarctica.
. . In Chile's Atacama desert, a UK-funded large observatory is nearing completion. Vista (Visible and Infrared Survey Telescope for Astronomy) will use infrared wavelengths to detect objects that are too distant or too cool to be seen using the visible spectrum. The steel structure that will hold Vista's primary mirror in place has now been shipped to Chile and installed inside the telescope enclosure. Scientists hope the first pictures from the telescope will come as early as next summer.
Aug 7, 06: A project aiming to create an easier way to measure cosmic distances has instead turned up surprising evidence that our large and ancient universe might be even bigger and older than previously thought. If accurate, the finding would be difficult to mesh with current thinking about how the universe evolved, one scientist said.
. . A research team led by Alceste Bonanos at the Carnegie Institution of Washington has found that the Triangulum Galaxy, also known as M33, is about 15% farther away from our own Milky Way than previously calculated. The finding suggests that the Hubble constant, a number that measures the expansion rate and age of the universe, is actually 15% smaller than other studies have found.
. . Currently, most astronomers agree that the value of the Hubble constant is about 71 kilometers per second per megaparsec (a megaparsec is 3.2 million light-years). If this value were smaller by 15%, then the universe would be older and bigger by this amount as well.
. . Scientists now estimate the universe to be about 13.7 billion years old (a figure that has seemed firm since 2003, based on measurements of radiation leftover from the Big Bang) and about 156 billion light-years wide.
. . The researchers reached their surprising conclusion after using a new method they invented to calculate intergalactic distances, one that they say is more precise and requires fewer steps than standard techniques.
. . The new method took 10 years to develop and relied on optical and infrared measurements gathered from telescopes all around the world. The researchers looked at a binary star system in M33 where the stars eclipsed each other every five days. Unlike single stars, the masses of paired stars can be precisely calculated based on their movements. With knowledge of the stars' masses, the researchers could calculate their true luminosities, or how bright they would appear if they were nearby.
. . The difference between the true luminosity and the observed luminosity gives the distance between the stars and Earth.
Aug 4, 06: A pair of strange new worlds that blur the boundaries between planets and stars have been discovered beyond the Solar System.
. . A few dozen such objects have been identified in recent years but this is the first set of "twins". Each has only about 1% the mass of Sol. Dubbed "planemos", they circle each other rather than orbiting a star. Their existence challenges current theories about the formation of planets and stars.
. . The pair belongs to what some astronomers believe is a new class of planet-like objects floating through space; so-called planetary mass objects, or "planemos", which are not bound to stars.
. . While they have similar masses to many of the giant planets discovered beyond our Solar System (the largest weighs in at 14 times the mass of Jupiter and the other is about seven times more massive), they are not thought to be true planets either.
. . The two objects have similar spectra and colors, suggesting that they formed at the same time about a million years ago. They are separated by about six times the distance between Sol and Pluto, and can be found in the Ophiuchus star-forming region some 400 light years away.
Aug 2, 06: A small wannabe star has emerged intact after being engulfed by a neighboring giant star, scientists say.
. . The victim was a brown dwarf, a failed star too small to sustain the nuclear reactions that ignites regular stars. The purpetrator was a red giant, an ancient star that once resembled Sol but which puffed up to enormous size after its hydrogen fuel was depleted. The red giant has since expelled most of its gas into space and transformed into a dense, Earth-sized star called a white dwarfs.
. . Astronomers spied the binary system that remains: the brown and white dwarfs. The brown dwarf is thought to have survived being swallowed by its companion during the white dwarf's red giant phase. Had it been less than 20 Jupiter masses, "it would have evaporated during this phase."
. . The discovery provides the first solid evidence that an object as small as a brown dwarf --which is just one step up from giant planet mass-- can survive another star's red giant phase. Previously, only red dwarfs, stars with masses about a third that of our sun, have been known to withstand such events.
. . The two dwarfs are separated by only a few thousandths the distance between Earth and the Sun and the objects rotate around in each other in about 2 hours. In the past, the two objects were farther part, but the temporary engulfment by the red giant's gas envelope is thought to have slowed down the orbital speed of the brown dwarf, causing it to spiral inwards.
. . Scientists think the failed star sped up its companion's red giant phase, the way enzymes speed up biological reactions while remaining unharmed.
. . "Normal single red giants that don't swallow anything probably last about 100 million years, but in this system, it may have only lasted a few decades."
. . In about 1.4 billion years, it will be close enough for the white dwarf to siphon gas from surface. When this happens, the brown dwarf will slowly shrink in mass, while the accumulating matter on the white dwarf will trigger massive thermonuclear explosions called novas every few years.
Aug 1, 06: Most of the roughly 200 known extrasolar planets are larger than Jupiter. Many complete their orbital years in just a few days. This proximity to their stars creates noticeable wobbles in the stars that make the planets detectable. Researchers have found a handful of star systems that could harbor life-bearing planets, in theory at least. A nearby star called 55 Cancri is one of the leading candidates.
. . The 55 Cancri system involves three gas giant planets and another world that could be icy or rocky and is about the size of Neptune. The setup is 41 light-years from Earth and about 4.7 billion years old, comparable to Sol.
. . Astronomers have said since 2002, when a planet was found at about the same orbital distance from 55 Cancri as Jupiter is from the Sun, that the star had the potential to harbor an Earth-sized world.
. . A new computer simulation shows that amid the giant worlds orbiting 55 Cancri, a small rocky world could indeed have formed --in theory-- and attracted enough water to support life as we know it. "Our simulations typically produced one terrestrial planet in the habitable zone of 55 Cancri, with a typical mass of about half an Earth mass."
. . Two other stars yielded little suggestion of habitable worlds. Another star, named HD 38529, is likely to support a belt and objects up to the size of Mars, the simulations indicate. Other modeling by Raymond has shown that only about 5% of the known giant-planet systems are likely to have Earth-like planets. But, he and others have said, there may well be many solar-type systems, in which the giant planets are all on the outskirts, that simply can't be detected yet.
July 27, 06: An enormous amoeba-like structure 200 million light-years wide and made up of galaxies and large bubbles of gas is the largest known object in the universe, scientists say. The finding will give researchers new insight into what the structure of cosmos looks like at the largest scale.
. . The galaxies and gas bubbles, called Lyman alpha blobs, are aligned along three curvy filaments that formed about 2 billion years after the universe exploded into existence after the theoretical Big Bang.
. . Some of the gas bubbles are up to 400,000 light years across, nearly twice the diameter of our neighboring Andromeda Galaxy. Scientists think they formed when massive stars born early in the history of the universe exploded as supernovas and blew out their surrounding gases. Another theory is that the bubbles are giant gas cocoons that will one day give birth to new galaxies.
July 26, 06: An extensive survey designed to find black holes has come up surprisingly short, leaving astronomers to wonder if their theories about these cosmic gravity wells are correct.
. . Many large galaxies are thought to be anchored by supermassive black holes. Since black holes can't be seen, researchers find them by noting how the gravity of one affects stars in the host galaxy and also by spotting X-rays that are kicked up as matter dives toward the black hole and is superheated.
. . The X-rays are particularly noticeable in galaxies that are shrouded in dust. And the X-rays are thought to be a prime contributor to a background of X-rays that permeates the universe.
. . "The hidden black holes we have found so far can contribute only a few percent of the power to the cosmic X-ray background", said study leader Loredana Bassani of the Italian research group IASF.
. . It could be, the researchers speculate, that in the local universe most supermassive black holes are mature and have had time to eat or blow away all the gas and dust that once enshrouded them, leaving them less likely to produce X-rays. Or, perhaps the undiscovered black holes are more hidden than astronomers realized.
July 24, 06: Young stars can spin around in half a day or less, compared to the 28 days it takes our more mature Sun to make a revolution. But young stars would spin even faster if something didn't hold them back. They spin so fast that, left unchecked, they would never fully contract and become stars.
. . We had to wait for Spitzer to see the disks." The orbiting Spitzer telescope sees the cosmos through infrared radiation, which makes it particularly good at finding the disks that swirl around stars, because the dust in the disks is heated by starlight and glows in infrared light.
. . Astronomers theorize that the disk slows the spinning star by pulling on its magnetic fields. When these fields pass through a dust disk, they are believed to get stuck "like a spoon in molasses".
. . Stars start out as collapsing balls of gas that spin faster as they shrink; as they spin, excess gas and dust flattens around them into pancake-like disks, which eventually clumps together to form planets.
July 24, 06: Newly detected dust found around the burst remains of a dead star could help reveal how planets and stars formed and how life began.
. . About 160,000 years ago, a star 20 times more massive than our sun erupted in a fiery explosion called a supernova. The star is in the Large Magellanic Cloud, a nearby dwarf galaxy. In 1987, the first light from that catastrophic event reached Earth and for several months, the supernova, dubbed SN 1987A, blazed as brightly as 100 million suns before fading again.
. . Now, nearly two decades later, astronomers have detected dust particles around the supernova that they think formed before the star exploded. The new finding is the first evidence that star dust can survive a supernova explosion. It is also providing a rare glimpse into a process called "sputtering", in which dust is eroded by interactions with superheated gas.
. . 1987A's newly detected stardust, found using an infrared telescope at the Gemini South Observatory in Chile, could help astronomers answer these questions. The dust particles are intermixed with superheated, X-ray emitting gas and found within an equatorial ring around SN 1987A. About a light-year across, the ring of gas and dust is expanding very slowly.
. . This suggests that the ring was created about 600,000 years before the star exploded, the researchers say. It is therefore unlikely that the ring was created by a supernova blast during the star's death, but rather by stellar winds when the star was still alive.
July 20, 06: It's been 46 years since Frank Drake aimed an antenna at the stars in the first modern SETI experiment. The number of star systems we've carefully examined is only about a thousand. That's a trifling sample compared with the several hundred billion suns that stud the Milky Way, and of little statistical significance. The speed of the experiments is growing geometrically. Every two years, the breadth of the search approximately doubles.
July 17, 06: For many millions of years after our universe first formed, no stars existed, and then there was one. That primordial star was likely a massive blazing behemoth that burned brighter and faster than any star around today.
. . A new computer model now suggests that it also formed much earlier than previously thought. Other studies have estimated that the first star sparked into existence some 155 million years after our universe exploded into life in the Big Bang 13.7 billion years ago.
. . The new simulation indicates that this event occurred much earlier, when the universe was only 30 million years old. It also suggests that it took about another 370 million years for the first galaxy as massive as our own Milky Way to form.
. . Even by stellar standards, the primordial star was a monster. It likely had a mass of about 100 times that of our Sun and it would have spewed out vast amounts of energetic radiation, especially in the ultraviolet range. It would have appeared blue-violet in color.
. . The first star shone brighter than most stars in existence today and it zipped through its stellar life in only 2 million to 3 million years, compared to the several-billion-year lifetimes that some of today's stars have. Our Sun is middle-aged now and has been around for 4.6 billion years.
. . Scientists think that when it spent its fuel, the first star exploded in a titanic stellar cataclysm called a supernova, flinging heavy elements forged during the star's lifetime into space, setting the stage for the next generation of stars.
The second generation stars likely formed within about a million years after the first, Barkana said. Within five million years, there were about 100 stars; within ten million years, 10,000 celestial orbs of fire were lighting up the heavens.
. . Unlike that first star, which was made up mostly of hydrogen and helium, the stars that came after contained heavier elements, such as carbon and iron.
. . Light once emitted by the first star might still be detectable, Barkana said. In space, the older an object is, the farther away it is. It would require a telescope about 100 million times more sensitive than the Hubble Space Telescope to observe light from the first star, but it's not impossible. we might have a chance to see the explosion with the instruments planned for the coming decade.
July 5, 06: Only two extrasolar planets have been seen directly, and there are no detailed images of any planet beyond our solar system. One way to tackle this problem is to place a shield, known to Sun-watchers as a coronagraph, "inside" the telescope. A huge daisy-shaped shield that would block out light from parent stars could be used to find Earth-like planets in other solar systems, an American astronomer said.
. . He and his team have designed a plastic "starshade" measuring 50 meters in diameter that would orbit in tandem with a trailing telescope and block out light from parent stars. "We will be able to study Earth-like planets tens of trillions of miles away and chemically analyze their atmospheres for signs of life." He added that if Earth-like planets exist, the starshade could find them within the next decade.
. . Three thrusters would be used to keep it steady while the telescope trailing thousands of miles behind follows light from distant planets as it hits the space shield.
June 21, 06: Black holes are known for their strong gravitational tugs, but gravity alone isn't enough to send matter tumbling into the center of one. Magnetism provides the final nudge, a new study finds. The research confirms a theory first put forth in 1973 that magnetic fields drive both the infall of matter into black holes and the production of light energy created by the process.
. . A black hole's gravity is enough to draw matter in and keeps it spinning in a stable "accretion" disk. But before it can take that final plunge, the material must lose some of its rotation speed, called angular momentum.
. . The spinning gas generates its own magnetic field, and this field powers a "wind" of charged particles blowing away from the black hole. The wind, which Chandra detected, transfers angular momentum from the inner regions of the disk outward. This slows down some of the spinning gas, allowing it to fall onto the black hole.
. . The magnetic field also causes turbulence and friction to build up within the disk. The friction heats up the gas to millions of degrees, causing it to glow brilliantly in the ultraviolet and X-ray bands.
June 13, 06: Astronomers have uncovered a frenzy of star forming activity in the dusty cores of two merging galaxies 250 million light-years away. They spied more than 200 mammoth star clusters in Arp 220 --a so-called ultra-luminous infrared galaxy, or ULIRG, and glows brilliantly in the infrared because its dust has been superheated by starlight.
. . The star clusters are packed into a very small region only about 5,000 light-years across. The biggest cluster contains nearly 10 million suns worth of matter and is twice as massive as any star cluster ever discovered in the Milky Way Galaxy.
. . If not for the thick layer of dust that enshrouds the entire galaxy, Arp 220 would shine 50 times brighter than our galaxy. It's the gas, however, that fuels star birth in the clusters.
June 12, 06: A ball of gas more massive than a billion suns is hurtling like an enormous comet through the interior of a distant galaxy cluster. The massive structure is held together by mysterious dark matter, astronomers said, but it is steadily breaking apart and becoming fuel for new stars. "This is likely a massive building block being delivered to one of the largest assembly of galaxies we know." [It's doubtless very very close to a vacuum; just big.]
. . The gas blob is moving at nearly 750 km per second relative to the galaxy cluster it is embedded within. Called Abell 3266, the cluster is itself moving away from us at a speed of nearly 17,000 km per second.
. . Nicknamed "comet" [jes' askin' for confusion!] the gas ball is the largest of its kind ever detected. It measures about three million light-years across, or around five billion times the size of our solar system. The gas is estimated to be about 10 million degrees C. Although this might seem hot to us, it is still relatively cool compared to some interstellar gas.
. . The gas blob is thought to have formed when two galaxy clusters --one large and one small-- collided billions of years ago. During the crash, a blob of relatively cool gas from the small cluster was sheared off and sent careening off into space on its own. During its travels, it got sucked in by the immense gravity of galaxy cluster Abell 3266, which it entered some 2 billion years ago.
. . The map shows gas being stripped from the gas comet's core and forming a large tail containing scattered clumps of cold, dense gas. The researchers estimate that about a sun's worth of mass is being lost by the gas comet every hour.
. . The gas ball is so massive that it could probably form it's own galaxy, but the researchers think the more likely scenario is that it'll add to the bulk of a giant elliptical galaxy already forming.
June 8, 06: A ghostly blue blob amid a swarm of red dots in a new cosmic image is the superhot intergalactic gas permeating the space within the most distant cluster of galaxies found to date. Intergalactic gas in the record-setting cluster glows with powerful x-ray emissions at a temperature of 10 million degrees.
. . Located nearly 10 billion light-years away, Cluster XMMXCS 2215-1738 is being hailed by its discoverers as a tantalizing glimpse of what galaxy clusters were like at their earliest stages of formation. They can see hints of more tan 1,600 additional galaxy clusters waiting to be confirmed.
. . Individual galaxies have been detected at greater distances. But the newly discovered cluster contains several hundred galaxies bound together by mutual gravitational attraction. Since the universe is thought to be 13.7 billion years old, the record-setting cluster must have formed when the universe was relatively young. "Yet this distant cluster appears to be full of old galaxies!"
. . The total mass of the cluster is enough to contain 500 trillion stars comparable in mass to our Sun. That's a surprising stellar mass for a galaxy cluster to have achieved at such an early era in the evolution of the universe.
. . "The total number of clusters depends on the amount of dark matter there is", Nichol said. "So this will give us a wonderful measure of how much dark matter there is in the universe."
June 7, 06: Scientists have detected large amounts of carbon gas in a newly forming solar-type system around Beta Pectoris, a nearby young star. The finding explains why the star's planet-forming debris disk is enshrouded in a thick cloud of gas. This is a mystery that has vexed scientists for years. According to theory, the gas shouldn't be there at all. The star's radiation should blow the gas away, but carbon has specific atomic quirks that render it immune --it doesn't feel strong radiation pressure from Beta Pic's light the way that other heavier elements such as nickel and iron do. It absorbs most strongly in the far-ultraviolet range --a band that Beta Pic doesn't radiate much in.
. . The new finding raises the possibility that in a few million years time, Beta Pictoris could be home to bizarre alien worlds that sound like something dreamed up by astronomers who've read too much science-fiction.
. . "If carbon-rich worlds are forming in Beta Pictoris, they might be covered with tar and smog, with mountains made of giant diamonds", said Marc Kuchner, an expert on extrasolar planets also from Goddard.
. . In addition to diamond mountains, such planets might also have methane atmospheres like Saturn's moon Titan.
June 6, 06: A flurry of new images from ground and space telescopes is refining astronomers' ideas about the Milky Way's closest galactic neighbor, Andromeda.
. . The total amount of infrared light being emitted by Andromeda: an amount equal to 4 billion suns. The amount of light a star gives off depends on its mass, so researchers now estimate that the total mass of all the stars in Andromeda is equal to about 110 billion suns. Because most stars in the universe are small red dwarfs that are less massive than the sun, this translates to about a trillion stars. This number is in agreement with past estimates; for comparison, the Milky Way is thought to contain some 400 billion stars.
. . The new data also allowed the team to calculate how many new stars are born in Andromeda each year. This number turned to be surprisingly low, only about 0.6 solar masses per year on average. The Milky Way was recently estimated to produce about half a dozen stars annually.
. . The new finding implies that Andromeda’s inner disk has been around for at least 6 billion years, or nearly half the age of the universe, and that it might have existed relatively undisturbed for even longer.
. . Also known as Messier 31, Andromeda is only 2.5 million light-years away. At 260,000 light-years across, its disk is larger than the Milky Way's, which is about 100,000 light-years wide. Despite being bigger and containing more than twice as many stars, however, Andromeda is only about half as massive as our galaxy because it contains less dark matter.
June 5, 06: Scientists have discovered a correlation between the amount of heavy elements in giant Jupiter-like extrasolar planets known as "Pegasids" and their parent stars. The finding could help explain how giant gas exoplanets form and why they are so hard to detect.
. . So far, scientists have discovered more than 180 planets orbiting stars outside our solar system. Called Pegasids, or "hot Jupiters", these planets have [known] masses between 110 and 430 times that of Earth and are large enough to cause a dip in starlight when they transit their stars. By measuring this dip, scientists can calculate a planet's mass and radius and then use these values to determine other properties of the planet such as density.
. . Before the current study, scientists didn't know what the common thread linking the nine hot Jupiters was. The planets seemed to be a motley crew: two were larger than models predicted; six appeared to be made up of mostly hydrogen and helium
. . However, while comparing the mass of heavy elements, or "metallicity" of the Pegasids and the metallicity of their stars, researchers discovered a simple correlation: Pegasids born around stars that are as metal-rich as our Sun have large diameters--meaning they are large overall--but have small cores, while those orbiting stars with two to three times more metals than our Sun have small diameters but large cores.
. . The finding also helps explain why so few Pegasids have been found using the transit technique: Because most have relatively large cores, they are smaller than expected and are thus more difficult to detect as they pass in front of their parent stars.
June 5, 06: Planet-like objects floating alone through space harbor disks of material that could make other planets or moons, something like miniature versions of our solar system, astronomers said today. What exactly to call any of these objects and systems is up in the air, however. The definition of the word 'planet' has blurred even more.
. . In one new study, six objects ranging in heft from five to 15 times the mass of Jupiter were observed. None are bound to stars. All are young and have disks of gas and dust that resemble disks found around young stars. Our own Sun had such a disk, out of which asteroids, comets and planets formed, theorists say.
. . The scientists involved in the new research are calling the objects "planemos" --short for "planetary-mass objects"-- that were born in the manner of stars and do not orbit normal stars. Observations revealed infrared radiation from the dust disks. There are no conventional photographs of the objects. Last year, a group led by Kevin Luhman at Penn State found an isolated object about eight times the mass of Jupiter with an apparent disk of gas and dust.
. . Researchers detected four newborn planemos, just a few million years old, in a star-forming region about 450 light-years from Earth, a relative stone's throw in cosmic terms. Scientists also found a disk-skirted planemo interacting with a brown dwarf --a failed star-- even closer to Earth, just 170 light-years away.
. . Brown dwarfs are generally considered to be much bigger than Jupiter but not massive enough to jumpstart thermonuclear fusion of hydrogen, the process that powers real stars and makes sunlight.
. . The other study looked at another so-called planemo and found evidence for a dust disk. While clearly of planetary weight, at about eight times as massive as Jupiter, 2M1207b orbits a brown dwarf. Jayawardhana, who worked on this study too, said: "It is quite likely that smaller planets or "aster"oids could now form in the disk around each one." Such a planet-sized object might have been expected to be pulled into orbit around the brown dwarf, but instead the two revolve around each other, and both have the makings for more satellites of each!
. . Even Jupiter had a disk when it was young, and its dozens of moons were formed from the dust and gas it contained. However, Earth's rocky moon probably was born when our world collided with another heavenly body early on, and Mars' moons were planetisimals captured by the planet's gravity.
. . By using the term planemo, the researchers are purposely avoiding the debate over whether 2M1207b and the free-floating objects should be called planets. If a planemo is a planetary mass object, however, then why are Jayawardhana and his colleagues describing the setups they've found as miniature Solar-type systems rather than miniature Jovian-type systems? "You can perhaps describe it as a big Jovian system too", he said. "The reason we describe [them] as mini-solar systems is because the central objects probably formed more like stars than like planets."
. . Luhman, the Penn State astronomer, doubts the IAU will adopt the term planemo. He said it is so difficult to pin down the masses of these things that distinguishing between a planetary mass object and a certain brown dwarf is very challenging. It makes more sense, he said, to call them all brown dwarfs if they formed in isolation and are not true stars.
. . Whatever the terminology, the findings suggest a whole new world of cosmic possibilities. "The diversity of worlds out there is truly remarkable", Jayawardhana said. "Nature often seems more prolific than our imagination."
May 30, 06: Scientists at Duke and Rutgers universities have developed a mathematical framework they say will enable astronomers to test a new five-dimensional theory of gravity that competes with Einstein's General Theory of Relativity.
. . Charles R. Keeton of Rutgers and Arlie O. Petters of Duke base their work on a recent theory called the type II Randall-Sundrum braneworld gravity model. The theory holds that the visible universe is a membrane (hence "braneworld") embedded within a larger universe, much like a strand of filmy seaweed floating in the ocean. The "braneworld universe" has five dimensions --four spatial dimensions plus time-- compared with the four dimensions --three spatial, plus time-- laid out in the General Theory of Relativity.
. . The framework Keeton and Petters developed predicts certain cosmological effects that, if observed, should help scientists validate the braneworld theory. The observations, they said, should be possible with satellites scheduled to launch in the next few years.
. . The braneworld theory predicts that relatively small "black holes" created in the early universe have survived to the present. The black holes, with mass similar to a tiny asteroid, would be part of the "dark matter" in the universe.
. . The General Theory of Relativity, on the other hand, predicts that such primordial black holes no longer exist, as they would have evaporated by now. "When we estimated how far braneworld black holes might be from Earth, we were surprised to find that the nearest ones would lie well inside Pluto's orbit."
. . Petters added, "If braneworld black holes form even 1% of the dark matter in our part of the galaxy --a cautious assumption-- there should be several thousand braneworld black holes in our solar system."
. . The scientists showed that it should be possible to answer this question by observing the effects that braneworld black holes would exert on electromagnetic radiation traveling to Earth from other galaxies. Any such radiation passing near a black hole will be acted upon by the object's tremendous gravitational forces --an effect called "gravitational lensing." "A good place to look for gravitational lensing by braneworld black holes is in bursts of gamma rays coming to Earth."
May 27, 06: THE spooky link that can exist between quantum particles even when they are far apart could provide an unexpected way to detect the ripples in space-time known as gravitational waves.
. . Gravitational waves are set off by extreme events, such as supernova explosions, but they are weak and notoriously difficult to detect. Now a group of physicists is suggesting that the waves could leave their signature on "entangled" quantum particles lying in their path.
. . Entanglement is a weird quantum effect through which particles become intimately linked, so that measuring a property on one instantaneously affects the others, no matter how far apart they are. It is a fragile property that is hard to produce and manipulate, but this fragility may make entangled states sensitive enough to pick up the weak gravitational waves that have so far eluded other methods of detection.
. . However, Lloyd does not think that a gravitational detector based on entanglement is a realistic prospect, even after amplification. "It's a real effect, but an unbelievably small one", he says. "To get something observable you'd need a gravity field so large it would rip your lab apart."
May 30, 06: Amateur observations revealed the telltale periodic dips of a transiting object only 30% larger than Jupiter. The star itself is a near-identical twin of Sol. The star decreases in brightness by 2% for 3 hours every 3.9415 days — the companion's orbital period. The spectra proved that the star wobbles back and forth slightly as it's being tugged by a companion with 90±7% of Jupiter's mass.
. . XO-1b is the tenth exoplanet known to transit its star, and it's one of five whose stars are bright enough to enable detailed follow-up study. The planet is approximately 0.05 astronomical unit from its host star (1/20th the Earth-Sun distance), making it a "hot Jupiter" that is almost certainly unable to support life.
. . Its diameter is 1.3±0.1 Jupiters, and its density is only about 50% that of water, meaning it's less dense than any of the solar system's planets.
Seth Shostak, SETI Institute:
. . It's important to note that our first contact with an extraterrestrial society probably won't be their first contact.
. . We'll only receive a solid signal from technically accomplished societies at our level or beyond. So it's quite possible they've been engaged in planet-to-planet communication for centuries or millennia. Consequently, these societies could be using an established, galactic protocol for information interchange, an orderly way of doing things that it behooves us to imitate. Since this seems inevitable (think of the protocols for exchanging information on the internet), it would clearly be better for us to eschew transmitting. Listen first and learn the protocol. After all, we'll be new members in the galactic club.
May 24, 06: Telescope technologies are being developed that will probe the very faint light from Earth-like planets around distant stars for tell-tale signs of biology. These are the same "life markers" known to be present in light reflected off the Earth --called "earthshine". They include signatures for water, and gases such as oxygen and methane.
. . Wesley Traub, chief scientist on the US space agency's (Nasa) Navigator Program is hopeful Nasa will approve the funds necessary to launch a Terrestrial Planet Finder (TPF) mission some time in the next decade. It will comprise two space-borne observatories which will hunt down and study Earth-sized planets orbiting stars at distances where liquid water could exist and sustain life. Europe has a similar, ambitious mission under consideration known as Darwin.
. . Essential to these observatories' success will be a new generation of instrumentation capable of seeing past the blinding glare of the parent star to pick out only the faint light reflected off the distant world's surface.
. . It is a hard task --the parent star is likely to be a billion to 10 billion times brighter than its tiny companion-- but recent experiments at Nasa's Jet Propulsion Laboratory suggest the technologies are getting close to the sensitivities required.
May 23, 06: Three years of scouring the skies with a "homemade" telescope fashioned from commercially available parts has finally paid off for astronomer Peter McCullough. The team built their telescope, which they call the XO prototype telescope, from two commercially available 200-millimeter telephoto camera lenses. It cost about $60,000.
. . First came the observation of the brief but telltale dimming of a Sol-like star 600 light-years away, then the detection of the star's wobble indicative of an orbiting planet's presence. Finally, McCullough's international team of professional and amateur astronomers received the official word that they had discovered a planet with a mass was slightly less than that of Jupiter.
. . "Of the planets that pass in front of their stars, XO-1b is the most similar to Jupiter yet known, and the star XO-1 is the most similar to our sun", said McCullough, of the Space Telescope Science Institute. "But XO-1b is much, much closer to its star than Jupiter is to the sun."
. . So far, of the roughly 180 extrasolar planets detected, including XO-1b, only 10 have been discovered using the transit method. Most have been spotted indirectly by noting a gravitationally-induced wobble in the host star.
May 22, 06: When the universe was young, countless dwarf galaxies formed, heating the universe and preventing the formation of more small galaxies, a new study suggests.
. . The Big Bang, a theoretical beginning to the universe, is thought to have generated lots of hot stuff --electrons and hydrogen and helium ions. The material expanded rapidly. As space expanded, matter cooled, and the electrons and ions formed neutral atoms and absorbed surrounding light. This placed a dark curtain throughout space. The shadowy era is called the Dark Ages.
. . The Dark Ages ended when the first stars and galaxies formed and began to shine. Their light stripped electrons from neutral gases in the universe and produced charged ions, a process called reionization. During this time, the gas reionized and also heated.
. . Hot gas does not easily clump together to form stars and galaxies. If gas is very hot, you need a very massive collection of it with strong gravitational pull to attract enough additional matter to create a seed from which a galaxy can form.
. . Before the period of reionization, galaxies containing only 100 million solar masses of material could form easily. After this period however, more than 10 billion solar masses of material had to be assembled to make a galaxy. Therefore, the theory states that the formation of dwarf galaxies --containing up to several billion stars-- would have been suppressed during this era in favor of more massive collections of stars. "We now have evidence that this occurred...."
. . The researchers determined the masses of early galaxies by looking at the light emitted by quasars, very distant galaxies with bright cores powered by supermassive black holes. In the early universe, clouds of hydrogen absorbed the light from quasars. If there are larger and fewer galaxies, there is more variation in the absorption seen across various lines of sight.
. . "As an analogy, suppose you are in a room where everybody is talking," Wyithe explained. "If this room is sparsely populated, then the background noise is louder in some parts of the room than others. However if the room is crowded, then the background noise is the same everywhere. The fact that we see fluctuations in the light from quasars implies that the early universe was more like the sparse room than the crowded room. We found that fluctuations in light from quasars implied that the early universe was sparsely populated", Wyithe said.
May 17, 06: Scientists using a Chilean telescope have discovered a unique planetary system made up of three planets similar to Neptune orbiting a star a little more massive than Sol, the European Southern Observatory said. It is 41 light years away.
. . "The planet closest to the star is probably rocky and the farthest is the first exoplanet of that mass that is in the habitable zone of its star, meaning, where water could be found in liquid form", the observatory said in a news release. An exoplanet is a planet that orbits a star other than Sol.
. . The scientists used the High Accuracy Radial Velocity Planet Searcher, or HARPS spectrograph instrument, at the 3.6-meter telescope at the European Southern Observatory in Chile.
May 17, 06: Three medium-sized planets of roughly the same mass as Neptune have been discovered around a nearby Sun-like star, scientists announced today. The finding (May 18 Nature) marks a first for astronomers because previously discovered multi-planet solar systems besides our own contain at least one giant, Jupiter-sized planet.
. . The setup is similar to the Solar System in many ways: The outermost planets is located just within the star's habitable zone, where temperatures are moderate enough for liquid water to form, and the system also contains an asteroid belt. The newly discovered planets have masses of about 10, 12 and 18 times that of Earth, and they zip around the star in rapid orbits of about 9, 32 and 197 days, respectively.
. . Based on their distances from the star, two inner worlds nearest the star are rocky planets similar to a huge Mercury, the scientists suspect. The outermost planet is thought to have a solid core of rock and ice and shrouded by a thick gas envelope.
. . Recent observations by NASA's Spitzer Space Telescope last year revealed that HD 69830 also hosts an "aster"oid belt, making it the only other Sun-like star known to have one. When the belt was found, it was suspected that there might be an unseen planet that was shepherding the asteroids; it now seems that there is more than one shepherd. The researchers think the asteroid belt could lie between the two outermost planets or beyond the third planet.
. . The planets have not been photographed. They were found using the Doppler, or "wobble", technique. The technique has since been refined to the point where lower-mass planets can now be detected.
May 9, 06: Two dim dwarf galaxies are the Milky Way's newest-known galactic companions, astronomers studying a vast swath of the sky reported. This brings the total number of dwarf galaxies in the Milky Way's cosmic neighborhood to 14. But theorists believe there could conceivably be hundreds more. The little galaxy found in Canes Venatici is about 640,000 light-years from the Sun, a stone's throw, in cosmic terms.
. . The two newest discoveries are among 12 spheroidal dwarf galaxies; two more are the Large Magellanic Cloud and the Small Magellanic Cloud, a pair of irregular dwarfs. Even though they are close, these galaxies were hard to spot because they were so dim, a defining characteristic of dwarf galaxies. The new galaxy in Bootes is the faintest discovered, with a total luminosity of 100,000 Suns.
. . Some astronomers theorize that there should be hundreds of clumps of so-called cold dark matter --slow-moving subatomic particles left over from the earliest period of the universe-- orbiting the Milky Way.
. . A galaxy is considered a dwarf if it is less than 10% as luminous as the Milky Way, since luminosity is mostly a matter of the total number of stars.
May 8, 06: One of the biggest mysteries in cosmology could be explained by a controversial theory in which the universe explodes into existence not just once, but repeatedly in endless cycles of death and rebirth.
. . Called the cyclic universe theory, it could potentially explain why a mysterious repulsive form of energy known as the "cosmological constant" (lambda) and which is accelerating the expansion of the universe is several orders of magnitude smaller than predicted by the standard Big Bang model.
. . In a new study, Paul Steinhardt of Princeton University and Neil Turok of Cambridge University propose that the constant was once much larger, but that its value decayed with each incarnation of the universe.
. . Scientists are still not sure what lambda is. According to one popular idea, it is the energy of space itself. According to quantum physics, the seemingly empty vacuum of space actually contains phantom particles that continually blink in and out of existence like flecks of sea foam. These particles are fleeting, but their energies combine to give every cubic centimeter of space a certain amount of energy. According to general relativity, this "vacuum energy" produces an anti-gravitational force that pushes space —and the matter in it— apart.
. . But there is a problem: the lambda that scientists have detected is more than a googol (1 followed by 100 zeros) times smaller than what theory predicts. To explain such a large discrepancy, physicists have been forced to come up with ever wilder theories.
. . One idea is that the lambda is not really small, but only seems so because it is being cancelled out by another unknown force with near perfect precision. To date, though, no mechanism has been found that can cause this cancellation.
. . According to the so-called Anthropic Principle, certain features of the universe are selected by the requirement that observers—in our case, humans—can detect them. In other words, only in a universe where lambda is small can intelligent beings exist who can wonder why it is small.
. . In a cyclic universe, new matter and energy are created about every trillion years when two sheet-like "branes" (membranes) collide along an extra dimension of space. Branes are predicted by string theory.
. . Because there can be endless cycles, the universe would be far older than the 14.7 billion years that scientists currently estimate. This would allow ample time for lambda to shrink to what astronomers see now. Because a high lamda prevents the universe as we know it from forming, early cycles of the universe would have been void of galaxies, stars and life; only in later cycles, when lamda had decreased to a much smaller value, could matter coalesce to create the world we inhabit today.
. . Once the universe is emptied out, a weak attractive force brings our universe's two branes together in a cosmic collision. Each collision is essentially a new Big Bang that infuses the aging universe with new matter and energy.
. . Steinhardt says their crazy theory can be tested: the inflationary Big Bang theory predicts that gravitational waves produced at the end of inflation leave an imprint on the cosmic microwave background, a diffuse form of electromagnetic radiation that fills the universe. If future experiments show the polarization pattern produced by such waves, it would disprove the cyclic universe theory, ruling it out as a possible solution to the cosmological constant problem.
May 4, 06: A star once hidden by a stellar death shroud is the source of odd behavior of its companion supernova, a new study has found. The find has laid to rest lingering questions over how the supernova, known as SN2001ig, seemed to change its cosmic stripes within weeks while astronomers looked on. "It was quite satisfying to be able to hold up a picture and see that there was a companion star right where we predicted."
. . Ryder and his team suspected a companion star was to blame for SN2001ig's shift from a hydrogen-rich supernova, known as a Type II, to a Type I variety devoid of detectable hydrogen. Only a few such transition supernovae, dubbed Type IIb by astronomers, have been identified.
[Here's one fascinating idea I just ran across.] Oct 2004 - A NASA institute has selected a new University of Colorado at Boulder proposal for further study that describes how existing technologies can be used to study planets around distant stars with the help of an orbiting "starshade."
. . The concept by CU-Boulder Professor Webster Cash of the Center for Astrophysics and Space Astronomy was one of 12 proposals selected for funding by the NASA Institute for Advanced Concepts, or NIAC. Cash's proposal details the methods needed to design and build what essentially is a giant "pinhole camera" in space.
. . The football field-sized starshade would be made of thin, opaque material and contain an aperture, or hole, in the center roughly 10 meters in diameter to separate a distant planet's light from the light of its adjacent parent star, Cash said. A detector spacecraft equipped with a telescope would trail tens of thousands of kms behind the orbiting starshade to collect the light and process it.
. . Such a system could be used to map planetary systems around other stars, detect planets as small as Earth's moon and search for "biomarkers" such as methane, water, oxygen and ozone. Known as the New Worlds Imager, the system also could map planet rotation rates, detect the presence of weather and even confirm the existence of liquid oceans on distant planets, he said.
. . "In its most advanced form, the New Worlds Imager would be able to capture actual pictures of planets as far away as 100 light-years, showing oceans, continents, polar caps and cloud banks", said Cash. If ET rainforests exist, he said, they might be distinguishable from deserts.
May 1, 06: Observations of "starquakes" have allowed scientists to estimate the thickness of a neutron star's crust for the first time. Using a technique similar to seismology here on Earth, researchers estimated that the crust of a highly magnetic neutron star, called a "magnetar," is nearly 1 mile (1.6 km) thick and made of material so tightly packed that a teaspoonful of the stuff would weigh about 10 million tons on Earth.
. . Magnetars are neutron stars whose magnetic fields are thousands of times stronger than their brethren. Astronomers have detected only about a dozen such stars. A magnetar's magnetic field is equivalent to about a hundred trillion refrigerator magnets and so strong that it could slow a steel locomotive from as far away as Luna.
. . The researchers calculated the thickness of the magnetar's crust by comparing the frequencies of energy waves traveling around the star against those passing through its interior. They say the vibrations are similar to the undulating S-waves observed during terrestrial earthquakes. If an even larger starquake could be observed, it could provide a glimpse into what kind matter makes up a neutron star's core.
. . The interior of neutron stars has been a source of great mystery and speculation for scientists. The pressure and density inside a neutron star core is thought to be so great that it could harbor esoteric particles not apparent since the moment of the Big Bang.
. . One possibility, scientists say, is that the stars' interiors are home to unbound versions of the building blocks of protons and neutrons, called quarks. Even the most powerful particle accelerators on Earth can't muster up the energies needed to reveal free quarks.
May 1, 06: Astronomers have detected a pair of supermassive black holes that are closer together than any previously discovered. The two giants are dancing around each other with only about 24 light-years between them and are expected to collide in the very distant future. [batcha thot they were a lot closer than that...] "That's more than 100 times closer than any pair found before."
. . Scientists think that when black holes collide, they generate enormous amounts of energy—more than all the stars in the universe combined according to one recent model—and send out gravitational waves rippling through space-time in every direction. Such gravitational waves could be detected with the ground based Laser Interferometer Gravitational-Wave Observatory (LIGO) or the proposed Laser Interferometer Space Antenna (LISA) space mission.
Apr 23, 06: A new study finds that the supermassive black holes at the hearts of some galaxies are the most fuel efficient engines in the universe. The finding, made using NASA’s Chandra X-ray Observatory, is giving scientists insights into how supermassive black holes generate energy and how they affect the galaxies where they make their homes.
. . Inflowing matter that hasn't yet passed this point of no return can -—through friction and interaction with the black hole's strong magnetic field—- release energy in the form of either diffuse light or focused jets of energy. "Once gas comes within a distance about a million times larger than the event horizon of the black hole, it becomes gravitationally captured", Allen explained. "At this point the gas becomes fuel for the black hole engine."
. . The new study looked at nine supermassive black holes at the centers of elliptical galaxies; each one was about a billion times more massive than our Sun. The black holes were relatively old.
. . The researchers found that these "quiet" black holes released about 1,000 times more energy as jets than as light. The reasons for this are still unclear. Most of the energy in the jets is being emitted as radio waves, but in at least one of the black holes studied, the energy was in the form of more energetic X-rays.
. . As they race outwards from their parent black holes at nearly light speed, the jets carve out enormous cavities, or "bubbles",in the surrounding gas environment; some of these bubbles can be tens of thousands of light years across.
Apr 23, 06: Doomsayers and Chicken Little-types can now strike "deathray from a star" from their list of possible ways to die. A new study finds that the chances of a gamma ray burst going off in our galaxy and destroying life on Earth are comfortingly close to zero.
. . Gamma ray bursts, or GRBs, are focused beams of gamma radiation emitted from the magnetic poles of black holes formed during the collapse of ancient, behemoth stars. They can also form when dead neutron stars merge with each other or with black holes.
. . It's been speculated that if a GRB went off near our solar system, and one of the beams hit Earth, it could set off a global mass extinction. But in a new study, researchers found that GRBs tend to occur in small, metal-poor galaxies and estimated that the likelihood of one occurring in our own metal-rich Milky Way is less than 0.15%.
. . GRBs can last anywhere from a few milliseconds to several minutes and are one of the brightest, and potentially the most deadly phenomena in the universe. So powerful are these events that some scientists have speculated they could help explain the so-called Fermi Paradox: If the universe is teaming with advanced alien civilizations as some theories predict, then why have we never found any traces of them? One answer could be that events like GRBs turn galaxies into giant autoclaves that sterilize life forms on planets before they have can develop interstellar travel.
. . Planets need metals to form, so a low-metal galaxy --while more likely to have GRBs-- will have fewer planets and fewer chances for life. Woosley said that while he thinks it's unlikely a GRB will form in our galaxy, he wouldn't rule out the chances of such an event just yet.
Apr 18, 06: Einstein's general relativity predicts that when black holes merge, they will emit gravitational waves that distort the fabric of space-time like ripples spreading across a pond. "These mergers are by far the most powerful events occurring in the universe, with each one generating more energy than all of the stars combined." [Could this be what "dark energy" is?]
Apr, 06: B1508+55 is a spinning neutron star, or pulsar, currently located approximately 7,700 light-years from Earth. Using the Very Long Baseline Array Telescope, scientists found both its speed and position by measuring the powerful beams of radio waves it emits. They then calculated its trajectory across the sky (see image) and determined that it was born out of the supernova explosion some two and a half million years ago of a giant star in the constellation Cygnus. "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding." Moving at an impressive clip of more than 1,000 kilometers a second, the pulsar is on track to leave our home galaxy.
Apr 13, 06: The Giant Magellan Telescope bands together seven huge mirrors with sophisticated control mechanisms. Its primary collectors are like the petals of a daisy, with one symmetric mirror in the center surrounded by six off-axis partners, each distinctly lopsided in shape. The assembly will gather 4.6 times as much starlight as does one of the California Institute of Technology's two 10-meter Keck Telescopes, currently the world's largest.
. . To snap legible photographs of such planets, GMT will use advanced adaptive optics to make images that are 10 times as sharp as those from Hubble. Each primary mirror will focus its photons onto a separate, 1.1-meter secondary reflector, a thin membrane attached to 672 actuators. Computers will then cancel out much of the atmospheric blurring by making 1,000 subtle adjustments to the shape of each secondary mirror every second.
. . This past summer, Angel and his co-workers installed a similar adaptive optics system in the Multiple Mirror Telescope and demonstrated that it boosted the resolving power of the instrument to its theoretical maximum.
. . Although the GMT has high-profile partners backing it--including the Carnegie Institution, the Harvard-Smithsonian Center for Astrophysics and five major universities--it competes with several other mega-telescopes for funding. Two of the competing proposals would scale up the Keck's segmented mirror design. Caltech and others want to build one 30 meters in diameter. The European Southern Observatory is working out plans for a 1.2-billion-euro, 100-meter observatory that it has dubbed the OWL, for Overwhelmingly Large Telescope. "It may come to a shootout, with only one getting funded."
. . In recent papers, Angel has touted a plateau in central Antarctica at an altitude of 3,300 meters, called Dome C, as a near-ideal observing site. The polar base completed there last year has on average the least wind, the lowest temperatures, and the driest air of any human outpost.
. . Angel has analyzed the advantages of a 20-meter lunar telescope built in a crater near the moon's south pole by using a spinning pool of reflective liquid as a mirror.
Apr 11, 06: A Massachusetts observatory unveiled a powerful new telescope designed to capture possible light signals transmitted to Earth by extraterrestrials. The telescope is the first to be developed solely to search the skies for light pulses from aliens and will be able to cover 100,000 times the amount of sky covered by current equipment.
. . "Sending laser signals across the cosmos would be a very logical way for E.T. to reach out, but until now, we have been ill-equipped to receive any such signal."
. . Researchers say alien civilizations may be as likely to use light signals to communicate as radio transmissions. Visible light can form tight beams and could potentially convey information more efficiently.
. . The telescope can process the equivalent of all books in print every second. As it scans the sky it uses a type of camera that can detect a billionth-of-a-second flash of light. "We are going from looking at a few stars a night to an all-sky survey where over a year we will search the entire northern hemisphere."
. . The telescope cost about $400,000 to build. "They've done it on a shoestring budget by being clever."
Apr 10, 06: The Swift telescope is about to break the boundaries of our cosmic vision, to see the most distant objects ever recorded, its chief scientist believes. The Nasa space observatory has already looked nearly 13 billion light-years across the Universe to record the light from a cataclysmic star explosion. But Dr Neil Gehrels expects Swift to see even more distant events. The investigator says the telescope has the ability to observe perhaps the very first stars to shine in the cosmos.
. . The spacecraft is set up to catch gamma-ray bursts --the intensely bright but fleeting flashes of very high-energy radiation that signal some of the Universe's most violent happenings. Once detected, the observatory swings itself to look directly into a flash with X-ray and ultraviolet/visible telescopes. It will also call up other space and ground-based facilities to join the fray.
. . It is believed that when these blue stars switched on, they brought to an end a period of darkness; and also "fried" the neutral gas to produce the diffuse intergalactic plasma we detect between nearby stars today.
. . The caveat for Swift is that it sees stars at the ends of their lives, and there has to be a question mark over whether the redshift 8-10 era would be sufficiently mature to produce GRBs. "Swift has now seen a redshift 6.3, which is very encouraging because it shows that any time delay is of the order of a few hundred million years rather than a billion years."
Apr 10, 06: New findings are revealing how individual galaxies in galaxy clusters evolve over time, changing from chemically simple to complex and from spirals to smooth disks.
. . Galaxies typically form in groups of a few dozen. Our own Milky Way is a member of a collection of more than 50 galaxies called the Local Group. Galaxy groups can become members of even larger conglomerates, called galaxy clusters, which contain about 150 large galaxies and hundreds of small, dimmer ones.
. . Scientists have long figured that galaxies evolve in a hierarchical structure, with mergers fueling growth, forcing star formation, and altering structure. But the details of the process remain unknown. In particular, how galaxies smooth out over time is a mystery.
. . One study by researchers at Oxford University and the Gemini Observatory found that the chemical compositions of galaxies at the center of some of the largest clusters change over time.
. . When the researchers actually looked, however, they found that galaxies located in far away clusters --seen as they existed in previous epochs-- showed large variations in the abundance of elements such as oxygen and magnesium, while the chemistry of galaxies in close, young clusters were much less varied.
. . At the same meeting, Chris Moss from Liverpool John Moores University, presented new results that could solve the mystery of how the shape of galaxies in clusters transform over time from spirals into smooth disks.
. . For reasons still unclear, many galaxies have a spiral shape when they initially form. Yet over the past several billion years, many galaxies in clusters have changed from spiral to a smooth, or "lenticular", disk shape.
. . When do the collisions occur? The answer, it seems, is while galaxy groups fall into clusters. Moss and colleagues looked at infalling galaxies and found that most of their shapes were distorted and that their stars were forming at higher than normal rates. Between half and three-quarters of the galaxies were either very close to one another or appeared to have collided and were in the act of merging with a companion galaxy.
. . Scientists predict that the Milky Way will undergo such a collision with its neighbor Andromeda in about three billion years. When that happens, both will lose their spiral shapes and merge into one large elliptical galaxy.
Apr 6, 06: Two supermassive black holes have been found to be spiraling toward a merger, astronomers said today. The collision will create a single super-supermassive black hole capable of swallowing material equal to billions of stars.
. . A handful of similar setups have been observed in which black holes appear inevitably on a merger course. This pair, at the center of a galaxy cluster called Abell 400, was known to be close but their fate hadn't been determined.
. . "The jets are similar to the contrails produced by planes as they fly through the air on Earth", Sarazin said. "From the contrails, we can determine where the planes have been, and in which direction they are going. What we see is that the jets are bent together and intertwined, which indicates that the pair of supermassive black holes are bound and moving together." The two objects orbit each other every 455 days.
. . The event remained visible in the sky to the unaided eye for about a week or so. Skywatchers would now need binoculars or a small telescope to see it. However, the nova remains bright at wavelengths outside the visible spectrum.
Apr 6, 06: A nova that lights up in the sky every 20 years is the result of a small star exploding repeatedly inside the outer atmosphere of a larger star, astronomers said today. The eruptions are among the most unusual stellar death cries ever spotted.
. . The setup is called RS Ophiuchi, or RS Oph. It consists of a burned out corpse of a star known as white dwarf that is very dense and about the size of Earth. It orbits close to a huge, puffed up red giant, which is just one step away from collapsing into a white dwarf itself.
Hydrogen gas from the outer atmosphere of the red giant is lured by gravity to the smaller white dwarf. Every 20 years, enough gas builds up to create a runaway thermonuclear explosion on the white dwarf's surface. In less than a day, the otherwise dim star brightens to more than 100,000 times the luminosity of the Sun. Much of the gas is shot into space.
An amount of material equal to the mass of Earth was blasted outward at millions of miles per hour. "We estimate the gas exploded off the white dwarf to be about 100 million degrees, about six times hotter than the gas at the center of our Sun."
Apr 6, 06: When stars explode as supernova, they carve giant bubbles in space. The Solar System is enveloped by such a structure from a long-ago explosion. Now scientists have shown that our bubble is being pinched and bullied backward by another expanding bubble forged from multiple supernovas.
. . Our bubble is called the Local Bubble by astronomers. It's shaped like an hourglass. The bully goes by the name of Loop 1 Superbubble; it's the result of several exploded stars over the past few million years, researchers figure. Superbubble's outer boundaries are marked by hot, expanding gas that radiates low-energy X-rays.
. . Superbubble is expanding faster than Local Bubble, so it compresses an area of cool dense gas, known as the Wall, situated between the two shells. In fact, the new study concludes, this interaction is what gives our bubble the waist in its hourglass shape. The density of gas in the waist of the hourglass is four times more intense than elsewhere along the Wall. Pressure also peaks there.
. . From where we sit, the edge of the Local Bubble is at least 91 light-years away in one direction and 358 light-years in the opposite. Superbubble is 895 light-years across.
Apr 5, 06: The lobster is the inspiration for a new type of European X-ray telescope. The observatory is designed to have an extremely wide field of view --just as the crustacean manages with its vision. The animal achieves this using a huge array of tiny channels that focus light by reflection, rather than by bending it through lenses found in human eyes.
. . A UK-led team is now building a similar set-up for a telescope that will sweep the sky for sudden, violent events, such as black holes swallowing stars.
Apr 5, 06: Astronomers say they have spotted a cloud of alcohol in deep space that measures 463 billion km across, a finding that could shed light on how giant stars are formed from primordial gas.
. . The vast bridge-shaped cloud of methyl alcohol has been spotted in a region of our galaxy, the Milky Way, that is called W3(OH), where stars are being formed by the gravitational collapse of concentrations of gas and dust.
. . Around 130 organic molecules have also been identified so far in outer space, fuelling speculation that these complex molecules may have helped to sow the seeds for life on the fledgling Earth.
Apr 5, 06: Scientists think they have solved the mystery of how planets form around a star born in a violent supernova explosion, saying they have detected for the first time a swirling disk of debris from which planets can rise. The pulsar was once a giant star that collapsed in a supernova explosion about 100,000 years ago.
. . The discovery is surprising because the dusty disk orbiting the pulsar, or dead star, resembles the cloud of gas and dust from which Earth emerged. Scientists say the latest finding should shed light on how planetary systems form. "It shows that planet formation is really ubiquitous in the universe. It's a very robust process and can happen in all sorts of unexpected environments", said lead researcher Deepto Chakrabarty, an astrophysicist at the Massachusetts Institute of Technology.
. . He said the debris disk most likely formed from metal-rich material that failed to escape the supernova. The disk resembled that seen around sun-like stars, leading researchers to conclude it might spawn a new planetary system.
Apr 4, 06: New data confirms the age of the universe at 13.7 billion years and says that the universe is almost "flat" (that is, space is only curved a bit through a higher dimension). As for dark energy, Bean said the results are consistent with the simplest theory, a "cosmological constant" representing a fundamental property of space, meaning that dark energy has the same value at every point in space and time.
Apr 3, 06: Astronomers are getting the most out of Europe's XMM-Newton X-ray observatory by making it work even in those periods that might be considered downtime. Like all space telescopes, XMM follows an observing schedule, looking at an object for some hours before swinging away to study the next target.
. . But scientists have been leaving the "shutter" open as its slews across the sky for some lucky dip observations. The technique has thrown up thousands of brilliant X-ray stars and galaxies. "About a quarter of the sky has been covered in this way, and it's all for free - XMM was not designed in the first place to do this."
. . When XMM turns, it does so very quickly, passing over each point in the sky in only 10 seconds (compared with a normal "pointed" observation of a few hours). Nevertheless, even this very short exposure is enough time for XMM-Newton to detect thousands of sources in the sky --black holes, quasars, active galaxies and stars-- many of which have been observed for the first time.
Apr 1, 06: The collision of two superdense stars would produce the strongest magnetic fields in the Universe, scientists say. These would be more than a thousand million-million times the strength of Earth's magnetic field.
. . Its computer simulations fit with the theory that mergers of neutron stars drive some of the bursts of high-energy radiation that sweep across space. However, the group says more work is needed to explain the link in detail.
. . The study gives fresh insight into the mechanisms that could lie behind extremely powerful, split-second flashes of light called short gamma-ray bursts (GRBs). The space-borne telescopes Swift and Hete-2 have indicated the source of at least some of these 100-millisecond bursts could result from two compact, magnetized objects falling on to each other. Theory suggests these objects could be two neutron stars.
. . Although about the same mass as our Sun, neutron stars would be little more than 10km across. Such objects are expected to have intense magnetic fields anyway, but the new simulations show that a collision between a pair of them could produce something altogether more spectacular --and sufficiently intense to launch a GRB. GRBs have been one of the great unexplained phenomena in astronomy since they were first detected in the 1960s.
Apr 5, 06: Planets outside our solar system might form, phoenix-like, out of the debris circling a dead star known as a pulsar, researchers reported on after finding the makings for a planet near such a body. This could mean that planet-formation could be more common than previously thought, said Deepto Chakrabarty of MIT.
. . Most planets are thought to form around young stars, like the sun, from debris left over when the star formed. This cosmic dust and gas spreads out around the star in a wide ring known as a protoplanetary disk, and the planets are made when gravity causes the debris to clump together.
. . This occurs typically when stars still have plenty of nuclear fuel at their cores. However, research by Chakrabarty and colleagues found a disk around a pulsar, the remnant from a spent star which ran out of nuclear fuel and collapsed, tossing out debris as it died.
. . A pulsar is the densest known kind of object in the universe, packing the mass of a Sol-like star into a ball about 16km across, he said. A single teaspoon of its mass would weigh about 2 billion tons.
. . Anything around it would be inhospitably bathed in intense X-ray radiation and particle radiation of the sort that can only be achieved on Earth in a particle accelerator. The researchers were surprised that the dust disk could remain there without being promptly torn apart.
. . But infrared emissions from the disk showed solid material, such as dust grains, that add up to the mass of 10 Earths, Chakrabarty said. And dust grains have been the seeds of planets in other planetary systems outside our own.
. . No planets are in evidence around the pulsar the scientists studied, he said, but the fact that the disk has survived is significant.
Mar 24, 06: Astronomers have spotted what they think is evidence for the ignition switch that turns on super-bright galaxies called quasars.The trigger was likely the merger of two galaxies, researchers said today.
. . Quasars were first detected in the 1950s based on emissions of radio waves. Astronomers thought they were strange nearby stars. Later they figured out the brilliant beacons were billions of light-years away.
. . That's how they got the name quasar, which is short for quasi-stellar radio sources.bA quasar is, in fact, a large galaxy anchored by a supermassive black hole that is actively --very actively-- feeding on surrounding gas. The frenzy causes the gas to heat up and glow so brightly that it outshines the galaxy itself.
. . Computer simulations led by Tiziana Di Matteo of Carnegie-Mellon University in Pittsburgh, Pennsylvania suggest a specific mechanism that might have triggered the activity: The merger of two galaxies drives gas toward the central regions where it triggers a burst of star formation and provides fuel for the black hole. The inflow of gas releases a tremendous amount of energy, and a quasar is born.
. . The quasar's output dwarfs the rest of the galaxy and generates a superwind that drives material into intergalactic space. The Chandra data provide the best evidence yet for a quasar-produced superwind, the researchers conclude. After about 100 million years in this scenario, the superwind will drive all the gas out. The quasar phase will end and the galaxy will settle down to a relatively quiet life, more like the situation in the Milky Way.
Mar 22, 06: A team of astronomers has found a cold object that is neither star nor planet circling a star relatively close to Earth. The object, a cool brown dwarf orbiting its red parent star, sits about 12.7 light-years from the Sun, making it the third-closest such object known to date. It's the only such object found as a companion to a low-mass star.
. . The newly found brown dwarf has a temperature of about 750 degrees Celcius, and a mass between nine and 65 times that of Jupiter, researchers said. It also orbits its red parent at a distance 4.5 times that of the average separation between Earth and the Sun, or about 672 million km.
. . It's not the closest to Earth. Two others have been found around the star Epsilon Indi, which sits about 11.8 light-years from Earth.
. . Last year, researchers found a brown dwarf surrounded by a disk of material, hinting that the odd objects could spawn their own system of mini-worlds. [Imagine that! How warm are the planets? Is life possible when lit by only infra-red?]
Mar 17, 06: Scientists announced new evidence supporting the theory that the infant universe expanded from subatomic to astronomical size in a fraction of a second after its birth. The finding is based on new results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001 to measure the temperature of radiant heat left over from the Big Bang. This radiation is known as the Cosmic Microwave Background (CMB), and it is the oldest light in the universe.
. . Using WMAP data, researchers announced in 2003 that they had pieced together a very detailed snapshot of the universe as it was about 400,000 years ago, and that they had determined things like its age, composition and development.
. . The previous data showed that the universe was about 13.7 billion years old. It also revealed that it wasn't until about 200 (not 400) million years after the Big Bang that conditions were cool enough for the first stars to form. Scientists were also able to conclude, as the probe's observations show, in the most basic terms, the contents of the universe. Only about 4% of it is ordinary matter, with 22% composed of so-called dark matter -- which is not made of atoms, doesn't emit or absorb light and is only detected by its gravity -- and 74% made up of a mysterious dark energy, which scientists believe is making the universe expand now.
. . The NASA space probe has peered back in time to a bare instant --less than a trillionth of a trillionth of a second-- after the Big Bang, astronomers reported. "This tremendous inflation of the universe happened in much less than a trillionth of a second."
. . The WMAP mission --short for Wilkinson Microwave Anisotropy Probe -- detected light created in the early universe that has been traveling across the universe for 13.7 billion years. Back then, there were no planets, no stars, no galaxies, nothing but infinitesimal differences in temperature. WMAP's current picture of the neonatal universe looks like a flat oval with cool spots shown in blue and green and hot spots in red and yellow. White lines show polarization --the direction of the oldest light. It may have seemed empty, but these tiny temperature differences formed patterns that eventually clumped into all the physical features we know as matter, including Earth and everything on it. Fluctuations are thought to have led to clumping of matter that allowed the formation of galaxies.
. . The WMAP probe, an ungainly looking craft about the size of a minivan, was launched in 2001 from Cape Canaveral. Now about 1 million miles away from Earth, the probe's mission is expected to continue through September 2009.
. . Brian Greene, a physicist from Columbia University who wasn't involved in the research, called the new findings "spectacular" and "stunning. WMAP's data supports the notion that galaxies are nothing but quantum mechanism writ large across the sky."
Mar 12, 06: Scientists looking at three rare and radiant pulsating stars have found they each are surrounded by a fairly bright layer of matter, a "cocoon", that has never before been detected around stars of this kind. The astronomers think the cocoons form as the stars shed huge amounts of mass at a tremendously faster rate than normal stars like the Sun.
. . The cocoons are about two to three times larger than the stars and about 4% as bright --very bright considering that these pulsating stars themselves are incredibly radiant. One of the enveloped stars is 400 times brighter than Sol.
Mar 12, 06: Astronomers announced today the discovery of a frigid extrasolar planet several times larger than Earth orbiting a small red dwarf star roughly 9,000 light years away. The finding alters astronomers' perceptions of planetary system formation and the distribution of planets in the galaxy, suggesting that large rock-ice worlds might outnumber gas giants like Jupiter.
. . The newfound planet is about 13 times more massive than Earth and likely has an icy and rocky but barren terrestrial surface, and it is one of the coldest planets ever discovered outside of our solar system. It orbits 250 million miles away from a red dwarf star, which is about half the size of our Sun and much cooler. The orbital distance is about the same as our solar system's planetisimal belt is from Sol. Being so far away from a red dwarf means that its surface temperature is an inhospitable -201 C, about the same as Uranus.
. . Further analysis of the system revealed the *absence of Jupiter-like gas giants, and scientists suspect the system literally ran out of gas and failed to form any. This may have starved the newfound planet of the raw materials it needed to turn into a gas giant itself.
. . Planet formation theory predicts that small, cold planets should form easier than larger ones around big stars. A previous study suggests that about two-thirds of all star systems in the galaxy are red dwarf stars, so solar systems filled with super-Earths might be three times more common than those with giant Jupiters. "These icy super-earths are pretty common", Gould said. "Roughly 35% of all stars have them. Sun-like stars form Jupiters, while red dwarf stars form super-Earths. Larger A-type stars may even form brown dwarfs in their disks."
. . Astronomers discovered this latest planet, catalogued as OGLE-2005-BLG-169lb, with a technique called microlensing, an effect where the gravity of a foreground star makes a more distant star appear brighter.
Mar 11, 06: A new paper by three Italian physicists proclaims, rather boldly, to have solved the dark-energy problem, perhaps the most perplexing question in modern physics. Their solution? Neutrinos, ephemeral but numerous particles left over from the big bang. There are three types, or "flavors", of neutrinos, and the flavor of a neutrino can change through a process called mixing. According to the researchers, this mixing of neutrinos throughout the universe creates just enough energy to explain away dark energy.
. . Clearly, whether or not they have solved the dark-energy problem, telling everyone that they can quit looking for other explanations seems wildly brazen and premature. Perhaps we should wait for some experimental confirmation of your calculations first, eh, gentlemen?
Mar 8, 06: The most distant explosion ever recorded, signaling the birth of a black hole near the beginning of time, was more chaotic and lasted longer than astronomers would have expected. The event was first reported last fall. Today, scientists released new findings and an animation that depicts a strange sequence of events in which the explosion of a massive star first settles down but then fires back up several times toward the end. Astronomers speculate that the black hole did not form instantly, as theory predicts, but that it was a prolonged process. "This was a massive star that lived fast and died young."
. . The burst, named GRB 050904, originated 12.8 billion light-years away, which means it occurred 12.8 billion years ago and the light took that long to reach us. It erupted very nearly at the beginning of time—the universe is about 13.7 billion years old.
. . The event provides the first glimpse of a star when the universe was in its infant stages. Until now, only entire galaxies had been observed so far away. "Because the burst was brighter than a billion suns, many telescopes could study it even from such a huge distance."
. . The flaring of GRB 050904 is something not typically seen in closer bursts. That means the earliest black holes might have formed differently than those being born today, Burrows said. The difference could be because the first stars were more massive, or perhaps it's just because the cosmic environment was different then.
Mar 6, 06: A galaxy in Stephan's Quintet is rushing headlong into a cluster of neighboring galaxies at more than one million mph and generating one of the largest shock waves scientists have ever seen. The finding, made using NASA's Spitzer Space Telescope, gives astronomers a chance to see a galactic collision in action and could help explain why some galaxies are more luminous in the infrared than others.
. . Stephen's Quintet is a cluster of five galaxies located about 300 million light-years away in the constellation Pegasus. For decades, astronomers using optical telescopes have known that galaxies in the cluster had experienced encounters in the past and that some were colliding even now. But it wasn't until they used Spitzer's Infrared Spectrograph on the galaxy cluster that they could make out the details of what was happening.
. . They discovered that one of the galaxies, called NGC7318b, is currently falling toward three of the others at a very high speed and generating a giant shock wave, or "bow shock", in front of it. A bow shock is akin to the ripple raised by a boat's bow as it moves through the water.
. . NGC7318b is estimated to be moving at more than 873 km/sec and generating a colossal shockwave larger than our own Milky Way Galaxy.
The finding could lead to a better understanding of so-called Ultra-luminous Infrared Galaxies, which typically have infrared luminosities 100 to 1,000 times greater than the Milky Way.
Feb 27, 06: Because Earth is located on the same plane as the Milky Way’s disk, astronomers can’t look down upon our galaxy to study it the way they can for others, like Andromeda. So for a long time, even basic things about the Milky Way, such as its shape and size, were difficult to determine. Astronomers came up with a variety of ways to solve this problem. They invented tools that see in ways human eyes can’t, and devised clever measuring techniques.
. . Our picture of the Milky Way is constantly changing as technology improves and astronomers learn more about distant galaxies. The current picture is richer than even just a few years ago as astronomers have filled in knowledge gaps and added new details. They’ve recently learned, for example, that the mysterious dark matter saturating our galaxy is actually “warm”, and they verified by various indirect means the existence of a supermassive black hole at its center. Studies have also shown that the Milky Way is more massive, more crowded and its stars more lonely than previously thought.
. . The Milky Way is a member of a collection of more than 50 galaxies called the Local Group. In terms of space occupied, Andromeda, or M31, is the biggest galaxy in this posse, but the Milky Way is the most massive.
. . The halo is about 100,000 light-years in diameter and 1,000 light-years thick. This halo contains some 170 orbiting star clusters and about a dozen small galaxies. The gravitational tug of the Milky Way is so great that it can sometimes tear these passing satellites apart, stripping them of gas and even stars. One star cluster, Messier 12, is thought to have been robbed of as many as a million stars in this way.
. . Orphan stars stripped from their parent galaxies and clusters form streamer-like “tidal tails” or else they linger in the galactic halo, where they intermingle with other lone stars. These other stars are mostly ancient, around 12 billion years old and older, and they don’t rotate around the galactic center in any organized way.
. . Astronomers estimate that the Milky Way contains about 100 billion stars. Recently, however, this number was upped by about a billion after the discovery that very old, nearly invisible stars had escaped earlier detections. Most of the Milky Way’s stars are concentrated in a main disk, which lately has been described as a series of disks, none of which are entirely distinct, but instead overlap one another. The largest is known as the thick disk; this disk is fairly flat and spirals like a slow-spinning hurricane because of our galaxy’s rotation. Nestled within the thick disk is an even flatter disk of stars, known as the thin disk. The stars in this thin disk rotate even faster around the galactic center than those in the thick disk.
. . Further in is yet another disk, known as the extreme disk, where stars and clouds of gas are moving fastest of all. Sol makes one complete orbit around the galaxy about once every 225 million years. In contrast, stars near the galactic center complete a lap in a few million years or less.
The nearest star to our Sun is 4.2 light-years away. BUT! Roughly 10 million stars are known to orbit within a light-year of the galaxy's center.
. . The Milky Way’s suspected black hole is called Sagittarius A*, or Sgr A*, and is thought to have between 3.2 and 4 million times the mass of our Sun.
. . There are still vital details missing in our picture of the Milky Way. Current models insist, for example, that our galaxy should have as many as a thousand dwarf galaxies buzzing around it, each with between 0.01 percent to 10 percent the mass of the Milky Way. Yet only a relative few satellite galaxies and globular clusters have been found. One hypothesis is that these missing satellites are composed entirely of dark matter and therefore invisible to current technology.
. . The Milky Way will collide with Andromeda and cease to be a spiral galaxy in about three billion years.
Feb 24, 06: A new kind of cosmic explosion has been spotted in Earth's celestial neighborhood, and amateur astronomers in the Northern Hemisphere might be able to see it next week, scientists reported.
. . But when scientists first detected it with NASA's Swift satellite on February 18, the explosion was about 25 times closer and lasted 100 times longer than a typical gamma-ray burst. "This is the type of unscripted event in our nearby universe that we hoped Swift could catch", said Neil Gehrels, Swift's principal investigator.
. . The explosion originated in a star-forming galaxy about 440 million light-years away. This would be the second-closest gamma-ray burst ever detected, if indeed it is one. The burst lasted for nearly 2,000 seconds, or about 33 minutes, astronomers said in a statement. Most bursts last a few milliseconds to tens of seconds. It also was surprisingly dim.
. . Scientists at Italy's National Institute for Astrophysics found hints of a budding supernova --an exploding star-- when they saw the afterglow from the original explosion grow brighter in optical light. If it is a supernova, scientists will have an unprecedented view of one from start to finish. Scientists will attempt observations with the Hubble Space Telescope and Chandra X-ray Observatory. Amateur astronomers in dark skies might be able to see the explosion with a 40-cm telescope.
. . The eruption might portend an even brighter event to come, a supernova. If the eruption indeed precedes a supernova, then it would reach peak brightness in about a week, scientists said. If the event is indeed a supernova in the making, scientists may get the first look at one unfolding from start to finish.
Feb 23, 06: Astronomers have found that a diffuse X-ray glow in our galaxy is not generated by hot gas but rather it's radiating from old stars that have yet to be counted. There could be roughly a billion stars we didn't know about in the Milky Way, they said.
. . Researchers have measured the X-ray background, as they call it, for years. It is more pervasive than the milky optical haze that gives our galaxy its name. Scientists have assumed some of the X-rays came from unseen stars but the leading theory held that most of it was created by hot gas, which would explain the diffuse nature of the glow.
. . The research, based on a decade of data from NASA's Rossi X-ray Timing Explorer, suggests the galaxy is "teeming with X-ray stars, most of them not very bright, and that scientists over the years had underestimated their numbers."
. . One source is a paired-star arrangement called a cataclysmic variable. These setups involve one regular star and a burned out shell of a star called a white dwarf. The dwarf pulls matter from the companion, and the gas heats up and releases X-rays.
. . The other source: active stellar coronas. These also involve a binary arrangement, in which one star stirs up the other's outer atmosphere, or corona, causing flares akin to those produced by our Sun.
. . The unseen stars have not all been counted in the new study. The new accounting suggests there are about a million cataclysmic variables and about a billion of the active corona setups. To confirm the numbers, Swank said, will require the Chandra X-ray Observatory to make surveys of the central region of the galaxy that are 10 times more sensitive than what it's been tasked to do so far.
. . Astronomers estimate the Milky Way contains about 100 billion stars. [Down from 500, & 200?]
Feb 21, 06: Astronomers have determined the density and speed of dark matter in our corner of the universe. The finding helps bring dark matter out of the realm of the hypothetical and places scientists a few steps to closer figuring out what this invisible stuff that pervades the universe and holds galaxies together is made of. It also settles once and for all the question of which galaxy --our Milky Way or Andromeda-- is more massive. The winner: The Milky Way.
. . The findings showed that the galaxies contain about 400 times more dark matter than ordinary matter; it also showed that the dark matter particles cannot be packed together more tightly than the equivalent of 20 hydrogen atoms per cubic centimeter of space. "It's important to note this stuff is not hydrogen atoms, it's just how much it weighs."
. . This surprisingly low density means that the smallest possible volume of space that dark matter can occupy is a cube measuring 1,000 light years across with 30 million times the mass of the Sun. "We never find smaller amounts of dark matter or more concentrated dark matter."
. . By knowing the minimum volume that dark matter can occupy, the researchers were able to calculate other physical properties of dark matter. One of these properties was speed, which turned out to be about 9km/s. "That's about a million times faster than predictions."
. . The researchers also calculated dark matter's "temperature" --or at least, the temperature dark matter would have if it gave off heat like ordinary matter. One of the difficulties about studying dark matter, of course, is that it emits no light and gives off no radiation, including heat. If dark matter were made of hydrogen atoms, it would have a temperature of about 10,000 C --or hotter than the surface of the Sun. This temperature is much warmer than scientists had expected. Other theories predicted that dark matter particles were relatively sluggish and that their temperature might be as low as 1 degree Celsius.
. . The research also settles an old debate among astronomers about which galaxy, our Milky Way or Andromeda, is more massive. "We are almost exactly twice as massive as Andromeda." --but it has slightly less dark matter.
. . Scientists still have a long way to go before they figure out what dark matter is, but the new findings could help narrow the possibilities. The two most popular candidates for dark matter are hefty particles called supersymmetric particles and low-mass particles called axions. Supersymmetric particles are believed to be a family of particles that have masses ranging from hundreds to thousands of times that of an ordinary hydrogen atom.
. . Axions are believed to have a very small mass and to have been created in large quantities during the Big Bang. Gilmore said the new results seem to favor axions as making up dark matter, but it might also be that dark matter is made up of a variety of particles.
Feb 20, 06: Massive, dying stars vibrate like giant speakers and emit an audible hum before exploding in one of nature's most spectacular blasts, scientists say. A new model developed by Adam Burrows at the University of Arizona and colleagues suggests that sound waves, not ghostly particles called neutrinos, deal the final blow to stars before they become supernovas.
. . After it has burned for 10 to 20 million years or so, the star runs out of fuel and develops a dense iron core about the size of Earth. The iron core grows until its density becomes so great that it collapses under its own weight. The core contracts, but then almost immediately springs back again. This sudden rebounding action generates a shockwave that speeds outward. Scientists think it is this departing shockwave that triggers the supernova explosion.
. . The problem, however, is that in even the best computer simulations, the shock wave isn't powerful enough on its own to break through the dense layers of superheated gas that envelops the core. In the models, the shock wave stalls as if muffled by a blanket and the supernova explosion never occurs.
. . The simulation involves more than a million steps -—five times more than typical models-- and encompasses a full second or more of stellar death, from core collapse right up to the instant the star goes supernova. Other models typically simulate only the first few hundred milliseconds before the explosion. The team's model shows that after about half a second, the collapsing inner core begins to vibrate. After about 700 milliseconds, the vibrations become so energetic that they create sound waves with audible frequencies in the range of 200 to 400 hertz, or around middle C.
Feb 18, 06: Astronomers looking for extraterrestrial life now have a short list of places to point their telescopes. They include nearby stars of the right size, age and composition to have Earth-like planets circling them, scientists said. But cuts in federal funding mean that private philanthropists who pay for the bulk of their work may find out first when and if extraterrestrial life is discovered.
. . Margaret Turnbull of the Carnegie Institution of Washington released her "top 10" list of potential stars to the meeting. They will be the first targets of NASA's Terrestrial Planet Finder, a system of two orbiting observatories scheduled for launch by 2020. She narrowed down the list to stars that could have planets with liquid water orbiting them. "We want to see these habitable planets with our own eyes", she added. So the star cannot be too bright, or it will obscure the planet.
. . Variable stars, which grow hotter and cooler, probably would not be conducive to life, so they were thrown out, as were stars that are too young or too old. Some are too gassy to have spawned planets like Earth, which contains a lot of metal. Others have massive companions whose gravity could interfere with the steady conditions needed for life to evolve.
. . Turnbull's top 10 list includes 51 Pegasus, where in 1995 Swiss astronomers spotted the first planet outside our solar system, a Jupiter-like giant. Others include 18 Sco in the Scorpio constellation, which is very similar to our own sun; epsilon Indi A, a star one-tenth as bright as the sun; and alpha Centauri B, part of the closest solar system to our own. Her top candidate was beta CVn, a Sun-like star 26 light-years away.
. . Dr Turnbull had previously identified about 17,000 stellar systems that she thought could be inhabited. For stars to be considered in the shortlist, they had to be at least three billion years old --long enough for planets to form and for complex life to develop. Candidate stars also had to have at least 50% of the iron content of the Sun. If the atmosphere of a star is low in iron, it is likely there were not enough heavy metals present early in its existence for planets to form. Stars more than 1.5 times the mass of the Sun do not tend to live long enough to produce so-called "habitable zones". The Carnegie Institution researcher also removed from her shortlist any stars with a companion. These companion stars can interfere with the habitable zone.
. . Astronomers have put together a set of principles - called the Seti principles - that outline what should be done if a signal from an extraterrestrial civilization is ever detected. "The scientific community --and the world-- is told right away", said Gill Tarter, from the Seti Institute in California. "Before a decision is made to send a message back everyone will consult --that's in the ideal world."
Feb 18, 06: Hoping to unlock the mysteries of black holes and the Big Bang, a team of scientists from Japan and seven other countries has apparently detected its first neutrinos in a multiyear project underway in Antarctica. The IceCube project uses holes dug 2,500 meters into ice near the South Pole. The project was launched in 2002, but only detected its first neutrinos on Jan. 29, recording the faint flashes of light given off by the particles when they interact with electrons in water molecules. Yoshida said it was the first time neutrinos had been captured in a natural environment outside a laboratory.
. . Neutrinos are subatomic particles with almost no mass and no electrical charge that are associated with radioactive decay. They so rarely interact with matter that they can typically pass entirely through the Earth unobstructed. Scientists want to study the elusive particles because they may hold the key to understanding the explosion of super-massive stars, known as supernovae. They also may hold secrets to other distant celestial objects, as they are thought to remain relatively intact during their travel through space. But scientists say detecting neutrinos is tricky. It requires specialized equipment deep underground —-shielded by heavy layers of rock from constant infiltration by cosmic rays, which may interfere with detection.
. . By using the vast Antarctic ice cap as a shield against cosmic rays, the team avoids the often prohibitive costs of building a specialized water tank, which is part of the conventional design for such experiments. The team has placed 540 detectors in the ice so far —-about 10% of the planned total of 4,800. The plan calls for building an observatory 1 cubic kilometer in size by 2010, about 20,000 times the capacity of the Super Kamiokande neutrino detector in central Japan.
Feb 15, 06: A newfound type of rotating stars played peek-a-boo with astronomers, appearing and disappearing a few times each day.
The stars seem to act like faulty cosmic lighthouses, spinning and emitting brief and bright flashes of radio waves that are among the brightest objects in the sky, then disappearing from the heavens entirely. The new stars are called rotating radio transients, or RRATs. While the team found more than 800 pulsars, they discovered 11 of the previously unknown RRATs.
. . RRATs are a type radio pulsars, although they don't emit radiation as uniformly as the conventional version. RRATs fire off a flash from once every four minutes to once every three hours. Some flash even less frequently. Each blast lasts for just a few fractions of a second, so even if you combined an entire day's worth of flashes into one, it would total only about a tenth of a second. However short and infrequent, these sporadic bursts are exceptionally bright. "The flashes of radio waves are comparable with, or stronger than, the pulses from the brightest pulsars", said Andrew Lyne of the University of Manchester. "I guess that there are only a few dozen brighter radio sources in the sky."
. . "We expect the galaxy to harbor roughly 400,000 of these objects", McLaughlin said. "This is four times as many as conventional radio pulsars." Like a lighthouse beacon, the stars rotate and the beam of radio emissions crosses our line of sight very rarely. So finding the bulk of them will be a challenge.
Red dwarfs are very dim stars with masses about a third that of our Sun and are thought to make up as much as 85% of the stars in our galaxy. Astronomers think the reason red dwarfs are so abundant is that they are much easier to form than their larger counterparts.
Feb 15, 06: A developing star has been found to have two disks of material rotating in opposite directions. The discovery hints at a future solar system with planets going this way and that."This is the first time anyone has seen anything like this, and it means that the process of forming planets from such disks is more complex than we previously expected." The whole setup sits within a large, star-forming region where chaotic motions cause clouds to rotate in different directions. "We think this system may have gotten material from two clouds instead of one, and the two were rotating in opposite directions."
Feb 8, 06: Scientists have found evidence of two mega planetary systems —-giant stars enveloped by what appear to be huge disks of planet-forming dust. The appearance of cloudy disks around stars are believed to represent current or future planetary systems. Our sun is surrounded by the Kuiper Belt, a disk containing dust, comets and other bodies.
. . Astronomers say the latest findings through NASA's Spitzer Space Telescope were surprising because hot and massive stars generate violent particle winds and intense radiation that theorists previously figured would thwart planet-making. "Our data suggest that the planet-forming process may be hardier than previously believed, occurring around even the most massive stars.
. . The new stars are believed to be 30 to 70 times more massive than Sol --one so big its diameter exceeds the orbit of Mars. Because of the stars' size, scientists say the surrounding debris disks are larger versions of the Kuiper Belt and probably contain about 10 times more mass.
. . The star, about 70 times as massive as Sol, harbors a disk of material that looks strikingly like the planet-forming disks that surround other Sun-like stars. The two newfound disks contain sand-like silicates, which are the building blocks of the planet-growing process. One of the disks also shows signs of clumping. Scientists said the disks may have already formed planets.
. . Last year, Spitzer revealed a disk around a small, failed star called a brown dwarf. That dim object has just 0.008 times the mass of Sol.
. . If there are any planets, they won't last long. Massive stars live short lives and die explosively. While our Sun is middle-aged at about 4.6 billion years, R 66 and R 126 will each go supernova within a few million years.
Feb 7, 06: Last fall, a group of about 30 scientists from different fields got together in Mountain View, California for a workshop sponsored by the SETI Institute. The workshop was convened to answer a single question: are the planets orbiting red dwarfs habitable? SETI scientists will soon begin looking for radio signals from intelligent extraterrestrial life using the Allen Telescope Array and they wanted to know whether red dwarfs should be included in the list of stars to search.
. . Red dwarfs are believed to make up about 85% of the stars in the universe, but they are so small and so dim that scientists have traditionally ignored them as possible havens for habitable planets. One of the main objections was that the habitable zones of red dwarfs would be very narrow and very close to the stars. For a planet orbiting a red dwarf to be warm enough to have liquid water, it would need to be located closer to the star than Mercury is to our own Sun. At such a close distance, the planet would become tidally locked to the red dwarf the way Luna is to Earth. Any water existing on such a planet would be boiled away on the side facing the star and frozen solid on the other.
. . In recent years, however, new computer models have suggested that the situation isn't as impossible as it might seem. The models predict that if an orbiting planet had a thick enough atmosphere, heat could be redistributed from the lit side of the planet to the side that was dark.
. . As for the criticism that a red dwarf's habitable zone is very narrow, Todd Henry, an astronomer at Georgia State University, has an interesting view. Because there are so many more red dwarfs than stars like our Sun, Henry has performed calculations suggesting that if the narrow habitable zones of all the red dwarfs in our galaxy were combined, they would equal the habitable zone of the all the Milky Way's Sun-like stars.
Feb 6, 06: NASA has delayed two programs to search for planets capable of supporting life as the space agency instead focuses on developing a new manned spacecraft to return to the moon in the next decade.
The dual Terrestrial Planet Finder telescopes, originally scheduled to lift off in 2016 and 2019, will use the information by SIM to photograph those planets to look for evidence of life. That program has been indefinitely postponed. "I'm disappointed that our society can't put more resources into answering the glorious question of whether we humans are alone in this universe."
Feb 6, 06: Astronomers have for the first time put some real numbers on the physical characteristics of dark matter. An Institute of Astronomy, Cambridge, team has at last been able to place limits on how it is packed in space and measure its "temperature".
. . Astronomers cannot detect dark matter directly because it emits no light or radiation. Its presence, though, can be inferred from the way galaxies rotate: their stars move so fast they would fly apart if they were not being held together by the gravitational attraction of some unseen material. Such observations have established this dark material makes up about 80-85% of the Universe that is matter.
. . Using the biggest telescopes in the world, including the Very Large Telescope facility in Chile, the group has made detailed 3D maps of the galaxies, using the movement of their stars to "trace" the impression of the dark matter among them and weigh it very precisely. With the aid of 7,000 separate measurements, the researchers have been able to establish that the galaxies contain about 400 times the amount of dark matter as they do normal matter.
. . "The distribution of dark matter bears no relationship to anything you will have read in the literature up to now", explained Professor Gilmore. "It comes in a 'magic volume' which happens to correspond to an amount which is 30 million times the mass of the Sun. "It looks like you cannot ever pack it smaller than about 300 parsecs --1,000 light-years; this stuff will not let you. That tells you a speed actually --about 9km/s-- at which the dark matter particles are moving, because they are moving too fast to be compressed into a smaller scale. "These are the first properties other than existence that we've been able determine."
. . The speed is a big surprise. Current theory had predicted dark matter particles would be extremely cold, moving at a few millimeters per second; but these observations prove the particles must actually be quite warm (in cosmic terms) at 10,000 degrees.
. . The most likely candidate for dark matter material is the so-called weakly interacting massive particle, or Wimp. Scientists believe these are relic particles produced in the Big Bang.
. . "Having 'hotter' dark matter makes it harder to form the smallest galaxies, but does help to make the largest structures. This result will generate a lot of new research." Experimental crystal detectors placed down the bottom of deep mines are hoping to record the passage through normal matter of these hard to grasp dark matter particles.
. . The Cambridge efforts have produced an additional, independent result: the detailed study of the dwarf galaxies has allowed the scientists to weigh our own galaxy more precisely than ever before. "It turns out the Milky Way is more massive than we thought. It now looks as though the Milky Way is the biggest galaxy in the local Universe, bigger even than Andromeda. It was thought until just a few months ago that it was the other way around."
Feb 2, 06: Here's another bright idea, one that was pointed out by SETI pioneer Frank Drake and Stanford engineer Von Eshleman nearly two decades ago. You could use the gravitational lensing technique to build the mother of all radio telescopes. Well, actually, you don't have to build it; you merely have to get in position to use it.
. . All that's required is to bolt a small SETI antenna and radio receiver onto a spacecraft, and send it cruising to the lonely, outer fringes of our solar system - to about twenty times the distance of Pluto (for the quantitatively inclined, the minimum distance is 550 astronomical units). Once there, the antenna would look back towards the Sun --which at that distance appears only as a dim star. Nonetheless, the Sun would act as an enormous radio lens, amplifying any signals from star systems on the other side. Indeed, the effective size of this solar lens would be roughly thirty thousand times the collecting area of the gargantuan Arecibo Radio Telescope in Puerto Rico. It could detect a transmitter with the power of your local TV station at a distance of a hundred light-years, even if the alien broadcasters weren't beaming our way.
Jan 30, 06: For more than 200 years, astronomers thought that most of the stars in our galaxy had stellar companions. But a new study suggests the bulk of them are born alone and never have stellar company. Since planets are believed to be easier to form around single stars, the discovery could mean planets are more common as well.
. . Stellar surveys found that more than half of all Sun-like stars were part of multiple systems. For more massive stars, like O- and B-type stars, the number was estimated to be as high as 80%. A few stars, like the North Star, Polaris, have two or more companions. "The assumption was that because most bright stars were binaries, all stars would tend to be binaries." The catch, however, is that most stars in the Milky Way are not bright stars like our Sun, but dim, low-mass stars called red dwarfs.
. . Scientists estimate that red dwarfs make up to 85% of the stars in our Galaxy. These stars are about one-fifth as massive as the Sun and up to 50 times fainter. Red dwarfs are so dim that it's only been in the past decade or so that technology has improved to the point where astronomers can study them in detail. And they've found that only about 25% of red dwarfs have stellar companions.
. . Lada concludes that upwards of two-thirds of all star systems in the galaxy are single, red dwarf stars. The skew towards singleness only applies to red dwarfs, however. It's still true that more than half of the brighter, more massive stars in the galaxy have companions.
. . Observations have shown that the large clouds that serve as stellar nurseries for massive stars are more turbulent than small clouds where red dwarfs are thought to typically come from. It could be that this turbulence causes massive stars to form in groups of two or more. It's thought that when there are two or more stars, the gravitational forces between them hinder matter from clumping into cores dense enough to form planets.
Jan 26, 06: Astronomers last year spotted a star leaving the Milky Way Galaxy. Later, one or two more were detected. And today, researchers announced the discovery of yet two more outbound stars. With so many outcasts on record, astronomers now see them as a new class of astronomical object, intergalactic stars exiled from their home galaxies. The two newfound exiles are racing out of the galaxy at more than a million miles an hour, fast enough that the galaxy’s gravity will never reel them back in.
. . The same thing likely occurs in other galaxies, so intergalactic space is probably filled with wanderers. There might be a thousand Milky Way exiles-to-be lurking inside the galaxy and on outbound tracks. The galaxy contains about 100 billion stars, so finding the outcasts is no easy task.
. . To leave the galaxy, a star must somehow be accelerated outward. Here’s what astronomers figure can happen: A two-star system, called a binary, rounds the center of the galaxy where it is tugged apart by the tremendous gravity of the central supermassive black hole. One of the stars is captured, while the other is shot outward as if from a slingshot. The researchers figure a star is flung from the galactic center every 100,000 years or so.
. . The speeds of the stars were measured using the Doppler technique. They might be moving faster. In a couple of years, after enough time has passed to detect the proper motion of such faraway objects, their exact speed might be pinned down.
. . The main plane of the Milky Way Galaxy, where most of its stars reside, is about 100,000 light-years wide. Our solar system is in one of the outer spiral arms, roughly 26,000 light-years from the central black hole.
. . Both of the newfound outcasts are outside the galaxy's main plane but have yet to leave the halo, a bigger sphere of the Milky Way's influence that is perhaps 300,000 light-years in diameter.
Jan 25, 06: A new planet-hunting technique has detected the most Earth-like planet yet around a star other than our sun, raising hopes of finding a space rock that might support life, astronomers reported. It's about 5-1/2 times more massive than Earth --still small enough to be considered Earth-like-- orbiting a star about 20,000 light-years away in the constellation Sagittarius, close to the center of the Milky Way.
. . The planet takes about 10 years to orbit its parent star, a red dwarf which is similar to Sol but cooler and smaller. Predicted surface temperatures are minus 220 degrees Celcius. The planet's cold temperatures make the chance of finding life very unlikely.
. . To find this new planet --named OGLE-2005-BLG-390Lb-- the team used a technique called gravitational microlensing. This method uses a network of telescopes to watch for changes in light coming from distant stars. If another star passes between a distant star and a telescope on Earth, the gravity of the intervening star acts like a lens and magnifies the incoming light. When a planet is circling the closer star, the planet's gravity can add its own signature to the light. This kind of light signature was observed on July 11 by a group of telescopes participating in a project known as OGLE, short for Optical Gravitational Lensing Experiment, which sees more than 500 microlensing events each year.
. . They went to two other groups of telescope-using scientists, RoboNet and PLANET (Probing Lensing Anomalies NETwork), who eventually confirmed the presences of a previously unknown planet.
. . Astronomers have been discovering so-called extrasolar planets for the last decade, but most have used a method that looks for a characteristic wobble in stars caused by the unseen planets that orbit around them. This technique has been successful in finding Jupiter-type planets but few with Earth's mass. However, the microlensing technique may hold promise for detecting more planets like our own, in the habitable zone neither too torridly close nor frigidly far from the stars they orbit.
Jan 24, 06: A spinning black hole in the constellation Scorpius has created a stable dent in the fabric of spacetime, scientists say. The dent is the sort of thing predicted by Einstein's theory of general relativity. It affects the movement of matter falling into the black hole. The spacetime-dent is invisible, but scientists deduced its existence after detecting two X-ray frequencies from the black hole that were identical to emissions noted nine years ago. The finding will allow scientists to calculate the black hole's spin, a crucial measurement necessary for describing the object's behavior. [or, the speed of matter at the "event horizon" ("surface").]
. . Because it's very hard to get gas to behave the same way twice, it argues strongly that these frequencies are being anchored by the black hole's mass and spin.
. . Spacetime can be thought of as an elastic sheet that bends under the weight of objects placed upon it. The more massive the object, the more spacetime bends. If the massive object is also spinning, it causes spacetime to not only bend but to twist as well. Scientists call this effect "frame dragging."
Jan 23, 06: An unusually high number of galaxies are aligned along a single plane running through the center of the giant Andromeda galaxy. Scientists don't have a theory to explain why. Galactic cannibalism or dark matter may be responsible, researchers say.
. . The Andromeda galaxy is located at a distance of 2.5 million light-years away and is the nearest spiral galaxy to the Milky Way. Like our own galaxy, Andromeda is surrounded by numerous dwarf galaxy satellites. Many of these satellites are within 1.3 million light-years or less of the galaxy's main disk.
. . That nearly 80% of Andromeda's satellite galaxy mass is located within a single plane is highly unusual and can't be accounted for by traditional theories of galaxy formation. The Milky Way was found to contain two similar planes of satellite galaxies in the late 1980s.
Perhaps long ago, Andromeda swallowed a nearby orbiting galaxy but did a messy job of it; the galactic crumbs from that meal became Andromeda's satellite dwarf galaxies. Such instances of galactic cannibalism are common and are believed to play a major role in galaxy formation.
Jan 20, 06: Astronomers using the Green Bank Telescope in West Virginia have discovered a superbubble, & the fastest-spinning pulsar ever observed. The superbubble of hydrogen gas rises 10,000 light years above the Milky Way's plane. Astronomer Jay Lockman said it is not unusual for hydrogen gas to be driven outward from the Milky Way's plane. But he said whatever drove the superbubble out must have been unusually violent. "Finding this superbubble practically in our back yard is quite exciting, because these superbubbles are very important factors in how galaxies evolve." The pulsar was found in a globular cluster of stars called Terzan 5 in the constellation Sagittarius, about 28,000 light years from Earth.
. . It spins 716 times per second. At that speed, the pulsar could not be more than 30 km in diameter. "If it were any larger, material from the surface would be flung into orbit around the star", said Hessels.
. . Pulsars are spinning neutron stars that sling beams of radio waves or light around as they spin. Pulsars are left after massive stars explode, the NRAO said. Thirty-three fast-spinning "millisecond" pulsars have been found in the same star cluster.
Jan 19, 06: Debris disks discovered around two nearby stars look strikingly like the Kuiper Belt in the outer part of our solar system, astronomers said today. The disks were found in a survey of 22 Sun-like stars by the Hubble Space Telescope. By blocking out light from the central stars, Hubble was able to image dust and other material around the stars. The stars are about 60 light-years away, and the shape of their disks have astronomers pondering the long-debated possibility that our own Sun might have an as-yet unfound companion dubbed Nemesis.
. . Each of the two disks has a sharp outer edge that might be caused by an unseen companion star that gravitationally grooms the material. Our own Kuiper Belt, which contains comets, Pluto and other frozen worlds, is thought to have similarly abrupt outer bound.
. . Unlike younger stars with debris disks -—thought to be the stuff of planet formation—- these two stars are more than 300 million years old. Things have likely settled into somewhat stable configurations with planets and well-defined debris streams, perhaps similar to our own solar system, which is now 4.6 billion years old. "These are the types of stars around which you would expect to find habitable zones and planets that could develop life", said lead researcher Paul Kalas of the University of California, Berkeley.
. . The small sampling of debris disks that have been discovered shows they fall into two categories: those with a broad belt, wider than about 50 astronomical units (AU); and narrow ones with a width of between 20 and 30 AU and a sharp outer boundary, probably like our own Kuiper Belt. Most of the handful of known stellar debris disks seem to have a central area cleared of debris, perhaps by planets. Kalas and Graham speculate that stars also having sharp outer edges to their debris disks have a companion -—a star or brown dwarf—that keeps the disk from spreading outward, similar to how Saturn's moons shape the edges of some of the planet's rings.
. . The scenario has Kalas and his colleagues thinking that the Sun might also have a companion that keeps the Kuiper Belt confined within a sharp boundary. U.C. Berkeley physics professor Richard Muller has proposed such a star, which he calls Nemesis, but no evidence has been found for one.
Jan 19, 06: Debris disks discovered around two nearby stars look strikingly like the Kuiper Belt in the outer part of our solar system, astronomers said today. The disks were found in a survey of 22 Sun-like stars by the Hubble Space Telescope. By blocking out light from the central stars, Hubble was able to image dust and other material around the stars. The stars are about 60 light-years away, and the shape of their disks have astronomers pondering the long-debated possibility that our own Sun might have an as-yet unfound companion dubbed Nemesis.
. . Each of the two disks has a sharp outer edge that might be caused by an unseen companion star that gravitationally grooms the material. Our own Kuiper Belt, which contains comets, Pluto and other frozen worlds, is thought to have similarly abrupt outer bound.
. . Unlike younger stars with debris disks -—thought to be the stuff of planet formation—- these two stars are more than 300 million years old. Things have likely settled into somewhat stable configurations with planets and well-defined debris streams, perhaps similar to our own solar system, which is now 4.6 billion years old. "These are the types of stars around which you would expect to find habitable zones and planets that could develop life", said lead researcher Paul Kalas of the University of California, Berkeley.
. . The small sampling of debris disks that have been discovered shows they fall into two categories: those with a broad belt, wider than about 50 astronomical units (AU); and narrow ones with a width of between 20 and 30 AU and a sharp outer boundary, probably like our own Kuiper Belt. Most of the handful of known stellar debris disks seem to have a central area cleared of debris, perhaps by planets. Kalas and Graham speculate that stars also having sharp outer edges to their debris disks have a companion -—a star or brown dwarf—that keeps the disk from spreading outward, similar to how Saturn's moons shape the edges of some of the planet's rings.
. . The scenario has Kalas and his colleagues thinking that the Sun might also have a companion that keeps the Kuiper Belt confined within a sharp boundary. U.C. Berkeley physics professor Richard Muller has proposed such a star, which he calls Nemesis, but no evidence has been found for one.
Jan 12, 06: Two new studies suggest that planet formation around multiple star systems may be more common than previously thought. One study, lead by doctoral student Deepak Raghavan from Georgia State University, confirmed that 29 planet-harboring star systems also contained a second star; three actually had two companions and were triple star systems.
. . Theorists have long wondered if such setups could occur, given the complex gravitational situations involved. It was once thought that the strong gravitational forces from stars in double star systems interfered with each other's ability to form planets. But the new theoretical model by Boss' team shows that if the gravitational force from one star in a double star system is weaker than the other, then gas-giant planets can form. The process is believed to require less than 1,000 years --much shorter than previously thought. The model also suggests that there would be plenty of room for Earth-like planets to form close to the central star after the gas giants finished developing.
. . That's because binary star systems tend to be rule rather than the exception in our galaxy. It's estimated that up to two out of every three stars in the Milky Way are part of multiple star systems, many of them binary. If such systems can shelter both outer gas giant planets as well as inner Earth-like planets, then the odds of finding habitable planet in distant star systems would be increased by roughly threefold.
Jan 12, 06: The universe's expansion underwent an unexpected braking in its first billion years, an astronomer suggested. The report throws a curve at an idea first proposed by Einstein that cosmic expansion occurs at a constantly increasing rate known as the cosmological constant.
. . But the motion of distant, massive exploding stars called gamma ray bursts suggests something is amiss, says astronomer Bradley Schaefer of Louisiana State University in Baton Rouge. "The first results point in the direction of the cosmological 'constant' not being constant."
. . Cosmologists created the term "dark energy" to describe the force pulling the universe apart at an accelerating rate. As far back as about 12.8 billion years ago, the universal expansion demonstrated by the motion of the bursts looks slower than in more recent times. That's a deviation from Einstein's prediction, Schaefer says.
. . If verified —-and that's a big "if", says cosmologist Michael Turner of the National Science Foundation —-the news would throw open the door to all sorts of "weird" theories about the true nature of dark energy, ones far different from anything supposed by Einstein.
. . Reaction from astronomers to the report, which Schaefer acknowledges as tentative, was cautious. Light from more distant parts of the universe may be disproportionately bent by the gravity of stars closer to Earth, another of Einstein's predictions.
Jan 11, 06: A telescope turbo-charger called ET has found its first planet outside the solar system, and something that looks like a suitcase in space is tracking possible faraway Earths, astronomers reported. These two small, relatively cheap instruments are part of a new wave of tools and techniques joining the accelerating race to find a world like ours that orbits a different star.
. . One is a "suitcase" in space --Canada's MOST satellite, a French mission called COROT is set to launch this year, and a NASA mission called Kepler is expected to launch in 2008. "We hope to search hundreds of thousands of stars in the next decade, for about 10,000 planets."
. . Scientists have detected more than 160 so-called extrasolar planets over the last decade.
Jan 10, 06: Scientists have found the first strong evidence that supermassive black holes at the hearts of some galaxies weren't born big, but grew to their monstrous sizes through the mergers of smaller galaxies. In the process, the researchers also revealed two distinct phases of galaxy evolution, including an early "tadpole" phase in which two galaxies merge.
Jan 10, 06: The bright star Vega is whirling so fast that its equator is several thousand degrees cooler than its poles, scientists said today. Its equator is cooler by 4,000 degrees F than at its poles. The finding, owing to a strange phenomena called "gravity darkening", confirms predictions about the star. It could also force scientists to rethink their ideas about the amount of light Vega is shining on a dusty debris ring, called the circumstellar disk, which surrounds the star's equator and is thought to be a potential birthplace for planets.
. . Vega makes a full rotation about its axis once every 12.5 hours. The Sun, in comparison, takes 27 days to make one rotation, even though it is much smaller than Vega. Vega is spinning at 90% of its critical rotation speed. Stars have a maximum speed, called the "critical rotation", at which they can spin. If stars exceed the critical rotation, the outward force caused by their spinning will overcome the inward gravitational force that keeps the star together. "If stars get to that limit, they will begin to fly apart." It bulges significantly at its equator: the star is nearly 23% fatter than it is tall. Because of the elliptical shape, gravity is no longer even across the entire surface. "For an ellipsoid, you actually have lower gravity when you're at the equator because you're farther away from the center of mass."
. . Vega is oriented in such a way that astronomers on Earth have only a pole-on view of the star. [think about it --if it's near north of us, we'd see it's "bottom".]
. . Based on the new results, the researchers estimate that the amount of light Vega's circumstellar disk receives is only about half of what was previously thought. The change could require scientists to rethink how much energy is being absorbed by the dust and gas that makes up the disk.
Jan 10, 06: A type of X-ray explosion found on neutron stars does not occur near black holes, scientists announced here today. The lack of explosions is strong evidence for the existence of a black hole event horizon, a theoretical boundary into which matter vanishes and cannot escape.
. . A neutron stars forms when a star 10 to 25 times more massive than our Sun runs out of fuel and expels most of itself into space. The remains, typically one or two solar masses, collapses into a compact sphere about 15 km across.
. . When stars with more than 25 solar masses collapse, they're thought to become black holes with infinite densities and no surfaces. A black hole is thought to be surrounded by an event horizon, a spherical region of space that extends about 50 miles from its center. Within the event horizon, the pull of gravity is so strong that nothing, not even light, can break free.
Jan 9, 06: One of the stellar companions of the North Star, Polaris, is clearly visible with a telescope, but the other hugs Polaris so tightly that it has never been directly observed until now. Using the Hubble Space Telescope, astronomers have photographed this close neighbor for the first time.
. . The newly observed companion star is about 2 billion miles from Polaris. Astronomers have known about it for about 50 years from analysis of light coming from the triple star system, but it was so dim compared to Polaris that direct observation was impossible.
. . "Our ultimate goal is to get an accurate mass for Polaris", Evans said. "To do that, the next milestone is to measure the motion of the companion in its orbit."
Jan 6, 06: Charon was discovered in 1978. It orbits so close to Pluto, at a distance of less than 20,000 kms that some astronomers have wondered whether they should be classified as a double planet system rather than mother and satellite. When a star's light passed the edge of Charon, researchers said it showed *no evidence of a substantial atmosphere.
. . Scientists are also thinking ahead to the next generation of space observatories. The Hubble space telescope has sent us captivating images of the deepest regions of space, but it has trouble imaging faraway planets, mainly because starlight drowns out any light coming from them. So the New Worlds Explorer will incorporate a massive shade to block unwanted rays. It will have such a high resolution that it could bring us our very first pictures of oceans or continents on extra-solar planets!
Jan 6, 06: Astronomers have the best evidence yet pinning down how just many stars form in our galaxy every year: about half a dozen. The research also indicates that a massive star explodes as a supernova in the Milky Way every 50 years on average. We're overdue, the scientists say. "Our galaxy isn't the biggest producer of stars and supernovae in the universe, but there's still plenty of activity." About 90% of the gas our Milky Way started with several billion years ago has now been converted into stars.
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