SPACE NEWS
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SPACE NEWS
of Extra-Solar Space
2005
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. . See also: Planetary Space (old) News.)
. . See the 2006 Solar-area news.
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See Go to "The Drake Equation" on
the likelihood of life elsewhere.
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Dec 27, 05: Astronomers using the Spitzer Space Telescope have discovered a perfectly decorated xmas tree 2,500 light years from earth. Scientists at the University of Arizona said the remarkable star cluster gives them the first glimpse of newborn stars acting just as predicted --patterned geometrically and spaced according to density, temperature and gravity.
. . "They're all about the same distance apart." The stars are less than 100,000 years old and located in a nebula. The "Christmas Tree Cluster" is about 1 to 3 million years old and too young for planets to have formed.
. . The observations reinforce British astronomer James Jeans' early 1900s gravitational collapse theory, and could yield clues to the formation of the Solar System. "We believe this process of forming stars in a cluster was exactly the same thing that happened with our very own sun 4 1/2 billion years ago. It tells us a lot about the history of the Solar System."
Dec 26, 05: Using recently discovered faint light echoes, astronomers have divined when three known supernovas occurred. The visible echoes are described as being much like sound echoes. They're created when light from the explosion expands outward and reflects off dust and travels toward Earth.
. . The explosions occurred centuries ago, the astronomers said, with the oldest having erupted about 600 years ago in Earth-time. All three occurred in the Large Magellanic Cloud (LMC), a satellite galaxy to our Milky Way. The LMC is about 160,000 light-years away.
. . The discoveries were not intended. Astronomers were surveying the region for signs of dark matter. In images taken years apart, researchers found concentric, circular-shaped arcs best explained as light moving outward over time and being scattered as it encounters dense pockets of interstellar dust. With each set of arcs, some geometric figuring shows they point back to supernova remnants that had been found previously by the orbiting Chandra X-ray Observatory, which spotted more recently emitted light from nearer to the objects. "Some relatively simple mathematics can help us answer one of the most vexing problems that astronomers can ask--exactly how old is this object that we are looking at?"
Dec 14, 05: A distant eruption of high-energy gamma rays is evidence for a black hole swallowing another dense object called a neutron star, astronomers announced today. A neutron star is a stellar corpse with a mass equal to a few suns packed into a space no more than 18 km across.
. . "For billions of years, this black hole and neutron star orbited each other in a gravitational tug-of-war", said Scott Barthelmy of NASA Goddard Space Flight Center. "The neutron star lost." Barthelmy and colleagues figure the neutron star was stretched into a crescent shape.
The flash of gamma rays lasted just a few milliseconds. Afterglows of X-rays, radio waves, visible and infrared light were detected thereafter. The afterglows are an important clue.
. . If the event, named GRB 050724, had been a merger between two neutron stars, there wouldn't have been so many crumbs left over. The two objects would smash, instantly form a black hole, and after a modest afterglow no more light would be seen, the astronomers theorize. Colliding black holes likewise should not generate much afterglow. Longer gamma-ray bursts, lasting seconds, are thought to signal the deaths of massive stars at the ends of their normal lives.
Dec 14, 05: The brightest star in our sky has a companion that's smaller than Earth, yet 98% as massive as the Sun, a new study reveals.
. . Astronomers already knew the brilliant blue-white Sirius had a stellar companion. But they didn't know the object's mass. The new measurement, announced today, was done by an international team of astronomers using the Hubble Space Telescope.
. . Sirius is one of the closest known stars at 8.6 light-years away. It is twice as massive as the Sun and has a surface temperature of 10,000 degrees C.
. . The companion, called Sirius B, is the scorching ember of a Sun-like star now called a white dwarf, and it's the nearest of its kind. The new observations also refined the measurement of Sirius B's surface temperature to be 25,000 degrees C. It was discovered in 1862 but close scrutiny is difficult because of the glare of the primary star. The white dwarf's mass was calculated by noting how its intense gravitational field alters the wavelengths of light emitted by the main star.
. . White dwarfs are the end products of explosions called Type Ia supernovas. "Measurements based on Type Ia supernovae are fundamental to understanding 'dark energy,' a dominant repulsive force stretching the universe apart", Barstow said. "Also, the method used to determine the white dwarf's mass relies on one of the key predictions of Einstein's theory of General Relativity; that light loses energy when it attempts to escape the gravity of a compact star." Light from the surface of the hot white dwarf has to climb out of this gravitational field and is stretched to longer, redder wavelengths of light in the process.
. . Sirius B, at just 12,000 km in diameter, has an intense gravitational field. A person weighing 68 kg (150 pounds) on Earth would weigh 25 million kg (55 million pounds).
Dec 13, 05: Dark matter makes up about 90% of the universe's total. Theory holds that it should gather with regular matter, because of their mutual effects of gravity. The new observations support that idea.
. . The work also supports the notion that dark matter is not made of particles that can collide. It's not known if dark matter involves particles at all, but if so, they must be collisionless.
. . The observations provide additional evidence supporting a leading theory that galaxies form in cosmic webs, with regular material and dark matter condensing into nodes something like water drops gather at intersections of spider silk.
Dec 12, 05: There's room in the universe for billions of galaxies, but that doesn't stop them from running into each other. New observations support the idea that galaxies are in constant interaction with each other and that the biggest ones get bigger by engulfing smaller ones.
. . Van Dokkum selected 126 nearby red galaxies, chosen because of their massive size, and began searching for signs of gravitational influence from outside sources, such as tails, broad fans of trailing stars, or other obvious asymmetries. Although these features are faint, they turned out to be quite common, showing up in 53% of the galaxies.
. . These observations also show that these merges happen fast --which is probably why they were difficult to spot before now. "Well, fast is a few hundred million years. That's fast compared to the age of the universe."
. . Galaxies smashing into one another sounds like an explosive event. On the contrary, they probably slide together smoothly, generating little fanfare. Galaxies are mostly empty space, and the distance between stars is so huge that the probability of stars colliding is actually very small.
. . There is still a chance for a violent explosion though, especially if the central black holes of the merging galaxies collide and merge. "This event could be so powerful that it could cause ripples in space time", said van Dokkum.
. . One would think that two galaxies mixing together would create a hot-bed for star formation. Cosmic gas is the fuel for star formation, and the idea is that the same tidal forces that pull these stars away from their galaxies will also compress the gas and lead to the formation of new stars
. . But collisions like these surprisingly spark very little, if any, new star formation. One possible reason is that the galaxy has already used up all its gas forming the stars already there. "Or, at a previous point, the central black hole created so much energy that it pushed the gas out of these galaxies", van Dokkum said. "That is what's next on the agenda to figure out."
. . It doesn't appear that the Milky Way has a collision-rich history, But that could change soon --the Andromeda galaxy M31 lurks just 2.3 million light years away and is on a crash course. "The Milky Way will collide in the future, in about 4 billion years."
Dec 2, 05: Newfound plumes of material 300,000 light-years across are forced outward by the explosive venting of a supermassive black hole, astronomers announced. Observations by NASA's Chandra X-ray Observatory revealed the energetic plumes of particles associated with a massive galaxy cluster called Perseus. The results provide evidence that a black hole can influence the space around it to intergalactic distances, researchers said. "In relative terms, it is as if a heat source the size of a fingernail affects the behavior of a region the size of Earth."
. . The Perseus cluster contains thousands of galaxies, all embedded in a giant cloud of superheated gas. The gas alone has the mass of trillions of suns.
. . The plumes, seen clearly in enhanced images from X-ray data, are low pressure regions in the hot gas extending outward from the central galaxy, NGC 1275, which is one of the largest galaxies in the universe. The low pressure is likely the result of the displacement of the gas by bubbles of unseen high-energy particles, Fabian's team reports. The bubbles appear to be generated by high-speed jets that shoot out from the supermassive black hole anchoring NGC 1275. Individual bubbles in the inner regions expand and merge to create vast plumes at larger distances.
Nov 30, 05: Since 80 of the 100 stars closest to the sun are red dwarfs, astronomers are interested in discovering if they have planets orbiting them. Of the currently known 170 planets circling other stars, only five of them are smaller than this newly discovered planet.
. . The discovery was made possible by a high precision instrument called HARPS.
Nov 30, 05: Astronomers have discovered a planet about as massive as Neptune orbiting one of the most common types of stars in the universe. The star is a red dwarf, a class of star about 50 times fainter than Sol. Among the 100 stars closest to us, 80 are red dwarfs. But astronomers had so far found only two planets in searches of about 200 red dwarfs, while well more than 150 planets have been found around other types of stars.
. . Gl 581 is located 20.5 light-years away, & is about one-third as massive as Sol.
. . The planet is about 17 times the Earth's mass and is one of the smallest ever found. It orbits close to its host star, completing a full circle in only 5.4 days at an average distance of about 6 million km. By comparison, Mercury is at a distance of 58 million km and completes an orbit in 88 days.
. . Even though the star is dim, the planet's proximity to it means its surface is probably about 150 degrees C (300 F), the researchers said.
. . The smallest known planet orbiting a normal star is about 14 times as massive as Earth. Planets about the same mass as Earth have been found around dying stars called pulsars.
. . Planets the size of Earth around normal stars will likely be detected with improved technology and future space missions, astronomers say. One theorist estimates there are 30 billion Earth-sized planets out there.
Nov 30, 05: The universe initially expanded rapidly, then slowed down, and then sped up again about 6.3 billion years ago.
. . Present age: 13.7 billion years.
Nov 30, 05: Astronomers have discovered what they believe is the birth of the smallest known planetary system. Peering through ground- and space-based telescopes, scientists observed a brown dwarf -—less than one hundredth the mass of the sun --just eight times the mass of Jupiter-- surrounded by what appears to be a disk of dust and gas.
. . The brown dwarf —-500 light years away-— appears to be undergoing a planet-forming process that could one day yield a planetary system. The new finding is the smallest brown dwarf to be discovered with planet-forming properties. If the disk forms planets, the resulting planetary system will be about 100 times smaller than our own, scientists said. It's about 2 million years old. Sol is about 4.6 billion years old.
. . "Here we have a Sun that is so small it is the size of a planet", he said. "The question then becomes, what do we call any little bodies that might be born from this disk: planets or moons?" "Some go by size, and others go by how the object formed", says study team member Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics. "For instance, this new object would be called a planet based on its size, but a brown dwarf based on how it formed."
Nov 21, 05: Astronomers are preparing to build the world's largest telescope that could be 100 times more powerful than the Hubble. The new TMT (Thirty-Meter Telescope) will be the first of a new generation of massive Earth-based telescopes that will far eclipse today's largest observatories.
. . It will be so large, it will be housed in an observatory the size of a football stadium resembling an eyeball. It will use nearly 800 individual mirrors. It will be the first realization of a new breed of super-scopes, known as Giant Segmented Mirror Telescopes. The higher elevations of Hawaii or Chile are under consideration.
. . A telescope's light-gathering power is an exponential function of its aperture. For example, a scope with a 100-meter aperture will collect 100 times more light than a 10-meter one, and will also have 10 times better angular resolution.
. . In addition to its giant aperture, the TMT's reflector will use advanced adaptive optics to compensate for the effects of atmospheric turbulence on the image. The mirrors will be kept in perfect alignment --within tolerances of 0.025 the width of a human hair-- by 1,700 servers, which will be automatically adjusted 750 times a second.
. . The TMT is expected to take 10 years to complete, and will take the title of world's largest telescope from Hawaii's Keck telescopes. How long it will hold that title, however, is another matter. A European consortium is looking at the feasibility of a couple of projects, known as the Euro50 and the OWL (OverWhelmingly Large) telescope --50 and 100 meters.
Nov 14, 05: Several theories have been proposed for star-formation. One predicts that low-mass stars accrete surrounding material. Another calls for the forceful combination of two protostars. A third, called the "collect-and-collapse" model, says that a parent massive star influences the formation of second-generation stars.
. . Now, a new collection of images provides the most complete and detailed evidence supporting the collect-and-collapse model, without ruling out the other models.
. . Collect-and-collapse works like this: When a star reaches a mass eight times greater than Sol, it begins to emit intense amounts of energy in the form of ultraviolet photons, triggering a series of events that lead to the formation of massive stars. These highly-energized photons react with surrounding gas molecules, and the region near the star becomes filled with ionized hydrogen gas. Once a region is acting this way, it becomes known as an HII region.
. . This ionized gas inside an HII region is hot. Like all hot things, it expands, and it does so continuously, since the area outside the region is much cooler. As the region expands, dust and gas begin to collect along the outer edges like a broom sweeping across a dirty floor. After a while, gravitational instabilities cause the dust and gas to fragment into clumps, which are large enough to collapse and form new, second-generation stars.
. . While many scientists subscribed to the collect-and-collapse model, no strong evidence existed until the release of this set of images.
Nov 10, 05: A new Hubble Space Telescope image reveals stars just in the process of being born amid a fantastic scene of wispy space structures and intense radiation. The stars have yet to condense into small enough packages to trigger thermonuclear fusion, which is what powers stars, but they appear to be on the verge, astronomers said.
Nov 9, 05: Giant clouds of gas and dust harboring embryonic stars rise majestically into space in a new picture from NASA's Spitzer Space Telescope. The image, dubbed the Mountains of Creation by astronomers, reveals hotbeds of star formation similar to the iconic Pillars of Creation within the Eagle Nebula, photographed in 1995 by the
Hubble Space Telescope. In both cases, the finger-like features are cool clouds of gas and dust that have been sculpted by radiation and fast-moving winds of charged particles from hot, massive stars.
. . Spitzer records heat, or infrared light, which penetrates the dusty clouds and allows a view of the star birth inside. In the largest finger, hundreds of embryonic stars not seen before are revealed. Dozens of stars-to-be are visible in one of the other fingers.
. . Many astronomers think our Sun was formed in a similar setup, then later migrated away from the clump.
Nov 2, 05: The most explosive star in our corner of the galaxy has a companion, astronomers announced today. "Until now, Eta Carinae's partner has evaded direct detection", said Rosina Iping, a research scientist at Catholic University of America in Washington. "This discovery significantly advances our understanding of the enigmatic star."
. . Eta Carinae is one of the most massive stars in the Milky Way, packing 100 times more material than Sol. It's visible from the Southern Hemisphere. Scientists have long expected that it was not alone. The huge star's strange behavior can best be described by putting another star into the setup.
. . Eta Carinae is thought to be too cool to generate X-rays, yet X-rays emanate from the region. Oddly, every five years the X-rays disappear for about three months. Astronomers theorized the X-rays were created when the outflow from Eta Carinae ran into the outflow from an unseen companion. Perhaps every five years, the thinking went, the orbits of the two stars put Eta Carinae in front of the collision site, as seen from Earth.
Nov 2, 05: Researchers from NASA's Goddard Space Flight Center in Maryland believe they have captured traces of radiation from long-extinguished stars that were "born" during the universe's infancy. The research represents the first tangible —-but not conclusive-— evidence.
. . The Big Bang, the explosion believed to have created the universe, is thought to have occurred 13.7 billion years ago. About 100 million years later, hydrogen atoms began to merge and ignite, creating brightly burning stars. Just what these stars were like wasn't clear.
. . Kashlinsky's team used NASA's Spitzer Space Telescope to measure the cosmic radiation, which is infrared light invisible to the human eye, in a small sliver of the sky. The team then subtracted the radiation levels of all known galaxies and suggested that the leftover measurements include radiation given off by those earliest stars.
. . the early universe was probably dark for half a million years. Later, hydrogen coalesced into brightly burning stars that were hundreds to a million times more massive than Sol.
Oct 21, 05: A NASA telescope has detected for the first time the building blocks of planets around brown dwarfs, suggesting that such failed stars probably undergo the same planet-building process. Until now, the microscopic crystal building blocks that eventually collide to form planets have only been seen around stars and comets —-considered the remnants of the solar system.
. . NASA's Spitzer Space Telescope recently spotted the tiny crystals and dust grains circling five brown dwarfs located 520 light years away. The crystals, composed of a green mineral commonly found on Earth known as olivine, are thought to be the building blocks of planets.
. . Brown dwarfs, like stars, form from thick clouds of gas and dust. But they collapse under their own weight and are considered the older and dimmer cousins to stars. The brown dwarfs in the study are all about 520 light-years away, in the Chamaeleon constellation. They range in mass from 40 to 70 times the heft of Jupiter. They are young, at roughly 1 million to 3 million years old. Analysis of the Spitzer data shows that the dust particles have crystallized and are sticking together.
Here is a short explanation of the new "nulling" technique for big telescopes.
. . Interferometers provide extremely good angular resolution. That means they are very good at sorting out which light waves come from which part of the star system. Additionally, an interferometer can be "tuned" so that the light coming from the exact center in the field of view (where the star is) will be blanked out or nulled, while the light from any other area will be viewed normally.
. . This setup may eventually help scientists select targets for NASA's envisioned Terrestrial Planet Finder missions. The success of those potential future missions, one observing in visible light and one in infrared, depends on being able to find Earth-like planets in the dust rings around stars.
Oct 18, 05: The idea that comets and meteorites seeded an early Earth with the tools to make life has gained momentum from recent observations of some of these building blocks floating throughout the cosmos.
. . Scientists scanning a galaxy 12 million light-years away with NASA's Spitzer Space Telescope detected copious amounts of nitrogen containing polycyclic aromatic hydrocarbons (PAHs), molecules critical to all known forms of life.
. . PAHs carry information for DNA and RNA and are an important component of hemoglobin, the molecule that transports oxygen through the body. They also make chlorophyll, the main molecule responsible for photosynthesis in plants, and – perhaps most importantly – they're the main ingredient in caffeine and chocolate.
. . While organic compounds have been discovered in meteorites that have landed on Earth, this is the first direct evidence for the presence of complex, important biogenic compounds in space. So far evidence suggests that PAHs are formed in the winds of dying stars and spread all over interstellar space. "And wherever there's a planet out there, we know that these things are going to be raining down on it. It did here and it does elsewhere."
Oct 17, 05: Sometime in the distant past, the dwarf galaxy M32 hurled itself at its much larger neighbor Andromeda, delivering an explosive uppercut punch that left a jagged hole nearly 10,000 light-years across in Andromeda's plane of stars, one that millions of years later has yet to fully heal.
. . New infrared images from NASA's Spitzer Space Telescope recently revealed the hole, which is hidden to optical telescopes behind Andromeda's veils of cosmic dust and gas. The Spitzer images also revealed other features of Andromeda that have never been seen before, including bright, new stars and spiral arcs swirling out from the galaxy's center.
. . Galactic collisions like that between Andromeda and M32 are actually quite common. In fact, Andromeda will collide with our own Milky Way Galaxy in about 3 billion years. The violence of that impact will make the M32 incident seem minor. Neither Andromeda or our own galaxy are expected to survive that collision with their spiral shapes intact. Instead, the two will merge to form a giant elliptical galaxy.
Oct 5, 05: The most intense explosions in the universe come in two varieties. One type lasts several seconds, and the others are gone in less than a second. Until now, astronomers had not pinned down the sources of the short-duration bursts.
. . New observations show convincingly that they are created by collisions of two very dense objects, likely neutron stars or a neutron star and a black hole, as theory had predicted. The results solve a 35-year-old mystery.
. . The explosions are called gamma-ray bursts, or GRBs. Several are recorded every day, coming from all directions of the sky. The afterglow of a single burst, measured in X-rays, radio waves and other wavelengths, can be billions of times brighter than the entire galaxy in which it originates.
. . Long-duration GRBs typically last about 20 seconds. Previous studies revealed one of these is released when the core of a young and very massive star collapses in a supernova event.
. . Astronomers have now observed two short-duration bursts in unprecedented detail and determined the likely scenario in which two dense objects collide and coalesce. The first burst was detected May 9 by NASA's Swift satellite. Scientists believed that morning that they were seeing, live, the merger of two neutron stars into a single black hole. Astronomers now know the event took place on the outskirts of a faraway galaxy, a location where old stellar remnants like neutron stars are known to reside.
. . Another important confirmation that came out of the observations: Short-duration GRBs are seen only when the jets of material that shoot from the merger are pointed at Earth. For every event we can spot, 30 other mergers go undetected.
. . "It's possible now that the first gravitational wave source that LIGO observes will also be a gamma-ray burst source", said Kevin Hurley of the University of California at Berkeley. "Now that would be a spectacular discovery."
Sept 26, 05: Astronomers have found the first evidence of cracks in a neutron star's crust. The star cracked when it was rocked by the strongest "starquake" ever recorded, researchers said.
. . Last December ('04), astronomers worldwide monitored the explosion that caused this starquake. The eruption was huge – in the first 200 milliseconds of the event the star released energy equivalent to what our Sun produces in 250,000 years. It was the brightest explosion ever detected outside of the Milky Way.
. . Now, scientists have used a collection of data from various satellites to provide the first observational evidence that the blast caused the star to form "cracks" several kms long. Scientists hope these cracks will provide a window into the mysterious interiors of neutron stars.
. . There are millions of neutron stars in the Milky Way galaxy alone, and some of these have magnetic fields trillions of times stronger than Earth's, the strongest of which are called magnetars.
. . This particular magnetar – SGR 1806-20 – is surrounded by the strongest magnetic field known in the universe. This could explain why the starquake –-caused when the magnetar's crust could no longer contain the magnetic stress building in the star's interior-– was so intense.
. . A magnetar's interior is a dense, liquid-like mix of neutrons, protons, and electrons – making it a terrific conductor of electricity. Because it has the characteristics of a fluid, it moves around a lot. The magnetar's magnetic field loops around the star, and all this movement in the interior messes with the field's shape, winding it up like you might do with a rubber band.
. . But the magnetar's exterior crust is not so pliable. The crust is made mostly of iron. The magnetic field passes through it in places, which isn't a problem for normal neutron stars. But in magnetars, the field interacts with the core and shifts around erratically, causing crustal stress. Eventually, the stress reaches the point where the crust cracks.
. . The first crack to form was five km long –-significant since this magnetar is only 10 km in diameter. Radiation spewed from this crack, causing a steep initial increase in detectable radiation. But that was just the beginning. Radiation continued to spill out of the star, but at a much slower rate than the initial burst. This suggests that: "Whether this is a set of long cracks, or a multitude of much smaller ones, isn't obvious to me", Schwartz said. "My hunch is therefore: one big one, followed by lots and lots of ongoing smaller ones."
. . SGR 1806-20 is 50,000 light-years away, but the blast was so huge it temporarily blinded some satellites and briefly altered Earth's upper atmosphere. A similar blast occurring within 10 light-years of our planet would fry Earth's ozone layer. But don't worry – the closest magnetar is 13,000 light-years away.
. . "Although we are looking back to when the universe was only 6% of its present age, this galaxy has already built up a mass in stars eight times that of the Milky Way."
Sept 26, 05: Astronomers using two of NASA's most powerful telescopes said they have detected a "big baby" galaxy, vastly heavy for its young age and its location in the early universe --800 million years after the Big Bang. The discovery was surprising, since astronomers have long theorized that galaxies form when stars gradually cluster together, with small galaxies preceding bigger galaxies.
. . But the stars in this cosmic infant --less than 1 billion years old-- have eight times the mass of those in the 13-billion-year-old Milky Way.
. . "It pushes back things like first light, which is the thing we are all hunting for."
Sept 20, 05: Stars race around a black hole at the center of the Andromeda galaxy so fast that they could go the distance from Earth to Luna in six minutes. The finding solves a mystery over the source of strange blue light coming from Andromeda's center. But it generates a new puzzle: The stars' phenomenal orbital velocity suggests they should never have formed in the first place.
. . Astronomers first spotted the blue light near Andromeda's core in 1995. Three years later, another group determined that the light emanated from a cluster of hot, young stars. Nobody knew how many were involved.
. . New data from the Hubble Space Telescope reveal more than 400 blue stars that formed in a burst of activity roughly 200 million years ago. The stars are packed into a disk that is just 1 light-year across. That's amazingly compact, by cosmic standards. "The blue stars in the disk are so short-lived that it is unlikely in the long 12-billion-year history of Andromeda that such a short-lived disk would appear now."
. . The stars are traveling at 1,000 km per second. They could circle the Earth in 40 seconds. The fastest among them orbit the center of Andromeda in 100 years. The stellar speed is controlled by the galaxy's central black hole. Such frenetic activity was thought to prevent star formation. "Gas that might form stars must spin around the black hole so quickly --and so much more quickly near the black hole than farther out-- that star formation looks almost impossible. But the stars are there."
. . The observations may provide clues to the activities in the cores of more distant galaxies that cannot be observed so well. At about 2.5 million light-years away, Andromeda is the nearest large galaxy to our own Milky Way.
. . The new observations also provide clinching evidence that Andromeda's central dark object is a black hole and not something else. It packs a mass of 140 million suns, the new study finds.
. . Ultimately, the strange goings-on in Andromeda may turn out to be commonplace. "The dynamics within the core of this neighboring galaxy may be more common than we think", Lauer said. "Our own Milky Way apparently has even younger stars close to its own black hole. It seems unlikely that only the closest two big galaxies should have this odd activity. So this behavior may not be the exception but the rule. And we have found other galaxies that have a double nucleus."
Sept 19, 05: Researchers have caught a star-turned-pulsar in the process of devouring its stellar neighbor, an act that accelerates its spin as it consumes more and more material. While they have about the same mass as the sun, neutron stars are much smaller, about 20 km or so wide. Sol, for comparison, is about 1.4 million km in diameter.
. . The find, made using two space-based observatories, marks the first time astronomers have witnessed a pulsar speeding up it strips material from a companion star.
. . Researchers found that the pulsar had already reduced its companion star to a size much smaller than that of the sun, leaving it with only 40 times the mass of Jupiter. Locked in a binary orbit smaller than the radius of the sun, the two objects complete a full cycle every 2.5 hours and are close enough to allow stellar cannibalization --known as accretion-- to occur.
. . But the process won't last forever. Eventually, the pulsar will completely devour its companion and be left to spin alone. "Accretion is expected to cease after a billion years or so."
Sept 14, 05: To maintain their fierce brightness, quasars must feed off the very galaxies they live within. That is why the discovery of a galaxy-less quasar is so surprising. Quasars are relatively small compared to the galaxies they outshine. They are only about the size of our solar system, but they can emit up to 100 times as much radiation as an entire galaxy.
. . Instead of a galaxy, the researchers detected a cloud of ionized gas about 2,500 light years in size near HE0450-2958. Dubbed "the blob", the researchers believe this gas cloud is what's feeding the black hole, allowing it to become a quasar. The researchers estimate that the quasar is siphoning off about one Sol's worth of mass each year from blob to satisfy its ravenous appetite.
. . Adding to the mystery is the detection of a deeply distorted galaxy located 50,000 light years away from the quasar. This so-called "companion" galaxy appears to be an extremely active stellar nursery, birthing new stars at a rapid rate, and it is also brighter in the infra-red spectrum than most galaxies.
. . The combination of these three factors --distorted shape, high rate of star production and ultra infra-red luminosity-- suggests to the researchers that the companion galaxy suffered a cosmic collision about 100 million years ago, possibly with the galaxy-less quasar. Such a collision would have stirred up dust and gas and enhanced the formation of stars.
. . Perhaps the most intriguing theory is that the quasar is encircled by a galaxy made up almost entirely of dark matter, a theoretical substance which is thought to make up 25% of the matter in the universe but which cannot be directly detected using current technologies.
Sept 14, 05: A supermassive black hole appears to be homeless in the cosmos without a galaxy to nestle in, Hubble Space Telescope scientists reported. Most monster black holes lurk at the heart of massive galaxies. But a team of European astronomers reported in the journal Nature that a particular black hole some 5 billion light-years away has no evidence of a host galaxy.
. . The black hole was detected when the scientists went hunting for quasars --extremely bright, small, distant objects that are strongly associated with black holes. Astronomers believe a quasar is produced by cosmic gas as it is drawn toward the edge of a supermassive black hole.
. . Most quasars and black holes are in the middle of supermassive galaxies and in their survey of 20 relatively nearby quasars, the scientists found 19 followed this expected pattern. But one showed no signs of having a galactic home.
. . This rogue black hole may be the result of a rare collision between a seemingly normal spiral galaxy and an exotic object harboring a very massive black hole.
. . One problem in quasar-hunting is that they are so bright, they outshine most galaxies that surround them, just as the headlights from an oncoming vehicle can make the vehicle hard to see. So even if a surrounding galaxy is present, it can be difficult to detect.
. . The European astronomers used the two telescopes to overcome this problem by comparing the quasars they were watching with a reference star. This let them differentiate the light from the quasar from the light from any possible underlying galaxy.
Sept 12, 05: An ancient, near-death star with a disc of metal-rich dust orbiting around it has recently been discovered by astronomers. The dust's origin is a mystery, though, as it should have been sucked into the star within a few hundred years of the star's death. Even though this anomaly is about 82 light-years away and several billion years old, astronomers think it could provide a preview of our solar system's future when the Sun dies five to six billion years from now.
. . Between three and five billion years ago, GD 362 was a star much like our Sun, only seven times more massive. It takes a lot of energy to maintain that much mass, and eventually GD 362's nuclear power plant ran out of fuel and the star could no longer produce enough heat energy to keep its outer layers from crashing inward. Once the fuel ran out, the star lost plenty of mass and heat, and shriveled into a white dwarf –-the final stage of star evolution where the star burns out and dies. Enough heat gets released during this process to vaporize any surrounding dust, rocks, and planets, leaving behind a disc of dust. This dust usually gets sucked into the newly formed white dwarf and incinerated within a few hundred years.
. . But when GD 362 went through this process five billion years ago, the dust never cleared up. And astronomers don't know how a dead star roughly the size of Earth has been able to sustain a disc the size of Saturn's rings for so long.
. . In five or six billion years, our own Sun will run out of nuclear fuel and begin turning into a super-hot white dwarf star. At that time, any of the planets and asteroids revolving around it might get crunched up into a giant dust disc.
Sept 12, 05: A team of international researchers announced today the detection of the farthest space explosion ever recorded, breaking the previous record by 500 million light-years. It occurred when the universe was less than a billion years old. Known as gamma-ray bursts (GRBs), the eruptions are giant flares of energetic gamma-rays that can last from less than a second to several minutes. "It's luminosity is such that within a few minutes, it must have released 300 times more energy than the Sun will release during its entire life of 10,000 million years."
. . Astronomers believe short GRBs that can last for only fractions of a second are generated when two massive objects, like black holes or neutron stars or even whole galaxies, collide, releasing tremendous amounts of radiation in the process.
. . The longer bursts, which can last for several minutes, are thought to be the final energetic emissions of massive stars that first undergo tremendous explosions called supernovas and before condensing into black holes.
Sept 8, 05: Thanks to the kick it received from a supernova, the fastest known neutron star is speeding out of the Milky Way. Most stars in the Milky Way lie in a fairly concentrated plane, varying only by plus or minus five degrees. Two-and-half million years ago, a massive star in the constellation Cygnus --a collection of giant stars within the galactic plane--went supernova. As the star collapsed, the resulting huge explosion gave a powerful "kick" to the neutron star that formed deep inside the supernova.
. . Now, at 52 degrees latitude and about 7,700 light-years from Earth, the neutron star B1508+55 is well out of the galactic plane. And although it's the fastest neutron star ever observed --traveling at 1,100 km/s, it could make the trip from New York to Los Angeles in under 4 seconds-- it will still be some time before it leaves the galaxy. "In maybe another million or so years it will leave what we nominally think of as our galaxy."
. . This discovery could settle the argument over how fast an imbalanced supernova explosion can send a neutron star flying. Three-dimensional computer models, run for the first time this past year, predict ejecting neutron star speeds of only 122 miles-per-second (200 km/s). In computer simulations, material from the outer layers of the collapsing massive star crashes into the neutron star as it's on its way out.
. . There is another way it may have gotten this much speed --binary disruption. Massive stars often exist in pairs, spinning furiously and held together by a band of gravity. When one of the stars goes supernova, this shock disrupts the gravity tie and sends both stars flying in opposite directions. "It doesn't look like you can get 1,100 km/s through this process", Chatterjee said. "Probably only 600 km/s from binary disruption. At 1,100 km/s, most people will say there must be a supernova kick involved."
Sept 1, 05: The most massive stars in our galaxy formed in a process much like that which created our sun, and not by cannibalizing young, small stars as previously thought, according to a new study. The stars in question are giants among giants --massive stars that weigh as much as 100 small stars like Sol, but because they are so rare and evolve so quickly, scientists were unsure how they achieved their colossal girths.
. . One popular theory was that they swallowed small immature stars called protostars in crowded stellar nurseries, but astronomers recently caught a massive star in the act of being born. Observations suggest it is developing through gravitational collapse, the same gradual process that built Sol.
. . Astronomers detected a gaseous disk surrounding the massive protostar. The disk contains 1 to 8 times as much gas as the Sun and extends outward for more than 42 billion km, eight times the distance to Pluto. Earth and the other planets in the solar system are believed to have formed from such a disk 4.5 billion years ago.
. . Astronomers also detected jets of bipolar gas spewing out from both ends of the HW2's circumstellar disk, a phenomenon previously observed only in the formation of low-mass stars like Sol. "Merging low-mass protostars woudn't form a circumstellar disk and a bipolar jet." If the cannibalizing theory of massive star formation were true, the spewing gas jets and the circumstellar disk would be destroyed as additional stars were swallowed.
Aug 28, 05: Researchers believe they have identified the main source of the cosmic dust that gets dumped on Earth –-meteoroids. A new study shows that grains of dust left in meteoroid trails are larger than previously thought. For a long time, scientists thought that these particles were just a few nanometers in size. Now, Andrew Klekociuk of the Australian Antarctic Division and his colleagues have studied the dust cloud from a recent large meteoroid and determined that the dust particles are actually 10 to 20 micrometers –-a thousand times larger than previously thought. "There is some uncertainty in the total influx of meteoric matter, but it is probably on the order of 20 to 60 thousand (old-)tons per year."
. . Depending on their size and overall number, cosmic dust and other particles in the atmosphere have the potential to change Earth's climate. They can reflect sunlight, which cools the Earth, absorb sunlight, which warms the atmosphere, and act as a blanket for the planet by trapping any heat it gives off. They can also facilitate the formation of rain clouds.
. . On Sept. 3, 2004 a large meteor –-estimated to have an original mass of a million kilograms-– crashed through the Earth's atmosphere, releasing more energy than a 15 kiloton nuclear bomb. Not only did this meteor leave bright streaks of fire as it tore through the atmosphere, it left behind a trail of meteoritic ‘smoke' or dust. The dust cloud stretched across altitudes from 35 to 11 miles (56 to 18 kilometers) and hung in sky for weeks.
Aug 23, 05: Black hole creation is crazier than previously thought, new observations reveal. Over the course of just a few minutes, as a massive star dies and a black hole is born, multiple explosions cause the black hole to powerfully eject matter as well as greedily consume it. It all starts with a gamma-ray burst –-the most powerful type of explosion in the universe and an indicator that a massive star is dying in what astronomers call a hypernova.
. . A surprising chain reaction ensues as the black hole forms from the collapsed remains of the star. "Stars are exploding two, three, and sometimes four times in the first minutes following the initial explosion", said David Burrows of Penn State University. "First comes a blast of gamma-rays followed by intense pulses of X-rays. The energies involved are much greater than anyone expected."
. . Before these observations –-made with NASA's Swift satellite telescope, which specializes in gamma-ray burst detection-– scientists believed that star death was a single explosion event. But that view changed once Swift went operational last November. Before the Swift telescope went up, scientists had seen hints of an "X-ray" bump about a minute after the initial GRB and before the final slow burnout known as the afterglow. But they couldn't catch it in time. Now, the Swift telescope automatically detects the first stage of the explosion and targets on the event in about one minute.
Aug 16, 05: New data from the Cassini spacecraft indicates that Saturn's trademark rings have their own atmosphere, separate from the gas around the planet they encircle. During close fly-bys of the rings, instruments on Cassini detected that the environment around the rings is atmosphere-like. More interestingly, though, is that the ring atmosphere is made up of molecular oxygen --two atoms of oxygen bonded together-- like that found in Earth's atmosphere.
. . The ice that makes up the rings is also the source of the oxygen that makes up this atmosphere. "As water comes off the rings, it is split by sunlight; the resulting hydrogen and atomic oxygen are then lost, leaving molecular oxygen." The ring atmosphere is probably kept in place by gravitational forces.
. . Saturn's atmosphere is 91% hydrogen by mass.
Aug 16, 05: Scientists have taken another step closer to explaining mysterious gamma ray bursts, some of the most energetic and bright explosions in the sky. Gamma ray bursts (GRBs) --the harbingers of death for some massive stars-- are intense blasts of energy and radiation that eject from massive dying stars.
. . GRBs are a two-step explosion. "The first burst of energy, lasting less than a few minutes, is produced by shockwaves within the collapsing star." The longer, less energetic afterglow is produced by collisions between ejected matter and the material around the star, witnessing the X-ray light curves in the transition period from prompt emission to afterglow. The soft X-ray afterglow following the initial GRB can last for periods ranging from hours to weeks. This afterglow was initially thought to be the slow fading of the initial burst.
. . But after closely observing five GRBs and measuring the patterns of X-ray emission, the INAF scientists determined that the afterglow was instead caused by violent shock interactions caused by the initial high-intensity blast.
Aug 16, 05: A new infrared survey that claims to be the most comprehensive structural analysis of our galaxy confirms previous evidence for a central bar of stars. The bar is embedded in the center of the galaxy's spiral arms and cuts across the heart of it all where a supermassive black hole resides. The survey found that the bar is longer than thought and sits at a sharp angle to the galaxy's main plane.
. . Seeing through the glow to determine the galaxy's structure is hard. Even more challenging is peering through all the dust between here there. The survey was done with NASA's Spitzer Space Telescope, which records infrared light. All objects that emit any heat can be seen in infrared, and this wavelength penetrates dust, so the new survey revealed light from tens of millions of stars hidden to optical telescopes.
. . The bar is made of relatively old and red stars, the survey shows. It is about 27,000 light-years long, or roughly 7,000 light-years longer than previously thought. Churchwell's team also found that the bar is oriented at about a 45-degree angle relative to the main plane of the galaxy, in which Sol and the other spiral-arm stars orbit. Bars are fairly common in large spiral galaxies, but some do not have them. Astronomers had glimpsed ours and were not sure if it was in fact a bar or perhaps an ellipse.
. . The main galactic disk is about 100,000 light-years wide, and Sol sits about 26,000 light-years from the center.
Aug 16, 05: A huge invisible bubble surrounds a well-studied black hole, scientists have just learned. The cavity is carved from space by the activity of the black hole itself and was detected with a radio telescope. Other space bubbles have been spotted, excavated by exploded stars and by supermassive black holes that anchor entire galaxies.
. . The most recent discovery is unique because it involves a stellar black hole, one that resulted from the collapse of a dead star here in our Milky Way. The bubble is formed by a jet of material streaming from the black hole at very high speeds.
. . Since this type of black hole is common, the finding suggests scientists have been "severely underestimating how much power black holes pump back into the universe", said the astronomers who announced the finding.
. . A jet from the hole travels around 15 light-years, at which point its pressure is balanced by the pressure of the surrounding interstellar gas, & forms the bubble there.
. . The newfound bubble is about 10 light-years across and is expanding at about 100 kps. Its creation has been ongoing for a million years or so. Astronomers are excited about the disovery because it is impossible to measure directly the power of jets like this one. By noting the interaction at the bubble, however, the researchers were able to calculate the jet's power. The jet packs about 100,000 times more energy than our Sun.
. . Astronomers suspect there are millions of black holes similar to Cygnus X-1.
Aug 8, 05: Over the past five years, NASA has spent $60 million delivering potable water to the International Space Station on the space shuttle (6 tons at a cost of about $40,000 per gallon). Deploying the Water Recovery System on the ISS will cut the volume of water hauled into space by two-thirds and free up enough room on the shuttle for four more astronauts.
Aug 4, 05: The Hubble Space Telescope has spotted of a collection of galaxies with more variety than a candy store. Some are big; some are small. Some are old; some are new. Some are nearby; some are far away. But one thing many of the hundreds of galaxies have in common is that they've never been seen until Hubble recently captured their light.
. . This image, which covers a patch of sky only a fraction of the area of a full moon, provides a typical view of the far-off places in the universe. As some of these galaxies are billions of light-years away in space, looking down this long corridor of galaxies is like looking billions of years back in time. The smaller galaxies are actually just further away and are faint because their light has taken billions of years to reach us.
. . The larger, brighter galaxies in the image are large, fully formed galaxies that are relatively close to us. Several of them are spirals with flat disks that are oriented either edge-on, face-on, or somewhere in between to Hubble. You can also see elliptical galaxies and other shapes with bars or tidal tails.
Aug 3, 05: A host of hidden black holes have been revealed in a narrow region of the sky, confirming astronomers' suspicions that the universe is loaded with many undetected gravity wells.
. . The most active black holes eat so voraciously that they create a colossal cloud of gas and dust around them, through which astronomers cannot peer. That sometimes prevents observations of the region nearest the black hole, making it impossible to verify what's actually there. These hyperactive black holes are called quasars. They can consume the mass of a thousand stars a year and are thought to be precursers to large, normal galaxies. The exist primarily at great distances, seen as they existed when the universe was young.
. . New observations with NASA's Spitzer Space Telescope cut through dust to spot quasars blocked by their own clouds, as well as other quasars hidden inside galactic dust. Spitzer records infrared light, which penetrates dust. It found 21 quasars in a small patch of sky. "If you extrapolate our 21 quasars out to the rest of the sky, you get a whole lot of quasars", said study team member Mark Lacy of the Spitzer Science Center at the California Institute of Technology. "This means that, as suspected, most super-massive black hole growth is hidden by dust."
Aug 1, 05: A star explodes every second or so, somewhere in the universe. It's how they die, and astronomers call the events supernovas. While much has been learned over the past few decades, supernovas remain somewhat elusive. Among the trickiest aspects of studying them is to spot a star exploding and figure out what kind of star it was before it fired. A new study of Hubble Space Telescope images reveals just the sixth example of a star that was identified before and after it went supernova. The problem, in part, is that the vast majority of supernovas that are spotted exist beyond our Milky Way Galaxy.
. . The progenitors of supernova explosions are red supergiant stars with masses eight to 15 times the Sun's mass. Stars with masses lower than eight times that of the Sun can't explode, scientists say. Instead, contract to white dwarfs and blow off their outer atmospheres.
July 28, 05: Most of the stars in our galaxy, and presumably all galaxies, are small red stars called M dwarfs. They are intrinsically very faint. The largest and brightest have about half the mass of the Sun but emit only a few percent as much energy as the Sun. The smallest are more than four thousand times fainter.
. . For decades, the conventional wisdom on M dwarfs and habitable planets was "forget it." The stars are so cool that in order for a planet to have liquid water, the planet would have to be so close to the star that it would become tidally locked. Just as the Moon is tidally locked to the Earth, the planet would have one side constantly in daylight and the other in perpetual night. It was thought that any atmosphere would freeze out on the night side, leaving the dayside completely exposed to radiation from the star. We cannot imagine life existing under those conditions. So, with few exceptions, M dwarf stars were excluded from SETI target lists.
. . In the mid-90's, people began to question the conventional wisdom. Atmospheric models showed that a tidally locked planet could not only retain its atmosphere, but distribute heat uniformly around the surface with a surprisingly modest amount of carbon dioxide. Other studies showed that ozone, a shield against harmful ultraviolet radiation, could be produced without biology on such a planet, making the surface more accommodating to life. Our conception of habitable conditions also expanded as we discovered "extreme life" (extremophiles) in amazing environments here on Earth. From boiling hot springs and deep ocean volcanic vents to frozen Antarctic lakes to the cooling water of nuclear reactors, life thrives in diverse environments. The environment on planets orbiting M dwarf stars may not be as hostile to life as we thought.
. . With those discoveries in mind, it seemed appropriate to reconsider the habitability of planets orbiting M dwarfs. The SETI Institute NAI team was awarded funding for a series of two workshops to consider the habitability of M dwarf stars' planets. More than thirty scientists attended the first workshop. After two and a half days of discussion, the consensus was that we could not rule out habitable planets orbiting M dwarfs but that a number of issues needed to be addressed.
. . Among the topics that need further study:
. . * Better data on the spectrum of solar flares. New studies of our local star will help us predict the effects of M dwarf flares on the atmosphere of a very close planet.
. . * Better measurements of stellar wind for M dwarfs. Mass loss due to stellar wind could be significant for these stars because they live so long.
. . * Better models for the evolution of a terrestrial planet over time, especially plate tectonics and the magnetic field.
. . * Better understanding of how the spectrum of the star, more energy in the red and infrared, will impact life.
We are confident that in early 2007, we should know whether M dwarfs make good target stars for SETI. That will be just in time for a new targeted SETI program on the Allen Telescope Array.
. . One other aspect of M dwarfs makes them intriguing for SETI. They may be ideal hosts for advanced technological civilizations because they live an extraordinarily long time. Stars like the Sun live, i.e., they fuse hydrogen into helium, for only about 10 billion years. No M-dwarf that ever formed has died yet; no M dwarf will die for more than another 100 billion years. With such long lifetimes, there are big possibilities for these small stars.
July 28, 05: They've discovered organic molecules --hydrocarbons-- in galaxies so far away they are seen at a time when our universe was just one-fourth its current age. So the raw materials for life were present long before the Solar System formed. Scientists do not know how life made the jump from organic material to biological material, so the finding says nothing about whether there is or ever was life elsewhere in the universe.
. . The galaxies are about 10 billion light-years away, so they are seen as they existed 10 billion years ago. Earth is 4.5 billion years old, and the universe has been around for 13.7 billion years.
. . "These complex compounds tell us that by the time we see these galaxies, several generations of stars have already been formed."
. . The large molecules, called polycyclic aromatic hydrocarbons, are made of carbon and hydrogen and are considered to be among the building blocks of life. They are common on Earth, forming naturally and also whenever you overcook a burger, drive your car, or somehow otherwise burn carbon-based material.
. . The hydrocarbons are also found throughout our Milky Way Galaxy. It is not too surprising to find them in more distant places, but scientists until now had not pinned down how early in the universe they formed.
July 20, 05: An unusually thick ring of dust around another star could hold clues about planet formation, say astronomers. The star, designated BD +20 307, is slightly more massive than Sol. The dustiest disk ever seen around a nearby star is probably the result of a collision between two small planets less than 1,000 years ago, they say. The researchers believe the collision may have been similar to the impact on the primitive Earth that formed Luna.
. . "I wouldn't be surprised if it was the result of a massive collision between planet-size objects." Because the star is estimated to be about 300 million years old, any large planets that might orbit it must have already formed.
. . The observations support the idea that comparable collisions of rocky bodies occurred here early in the Solar System's formation about 4.5 billion years ago. They could also lead to more discoveries of this sort which would indicate that the rocky planets and moons of our inner Solar System are not as rare as some astronomers believe.
. . Interplanetary dust reflects sunlight --the so-called Zodiacal Light.
July 18, 05: The biggest starquake ever recorded resulted in oscillations in the X-ray emission from the shaking neutron star. Astronomers hope these oscillations will crack the mystery of what neutron stars are made of.
. . On December 27, 2004, several satellites and telescopes from around the world detected an explosion on the surface of SGR 1806-20, a neutron star 50,000 light years away. The resulting flash of energy --which lasted only a tenth of a second-- released more energy than the Sun emits in 150,000 years. [!]
. . Just as geologists study the Earth's interior using seismic waves after an earthquake, astrophysicists can use the X-ray oscillations to probe this distant neutron star. The particles inside a neutron star are so tightly packed together that electrons are forced into the atomic nucleus, where they fuse with protons to make neutrons. This pure neutron material is so dense that a spoonful of it would weigh over a billion tons on Earth. A neutron star with the mass of our Sun would only be 15 km wide.
. . Neutron star "geology" is thought to involve a hard outer crust floating over a superfluid core. But the exact details are not known --like whether the core contains esoteric particles called strange quarks. Starquakes may provide the answer.
. . There are millions of neutron stars in our Milky Way galaxy. Some of these have intense magnetic fields, which are trillions of times greater than the Earth's magnetic field. On the high end of magnetic neutron stars are the magnetars. The magnetic field of magnetars is so strong that it sometimes warps the crust. This is the probable origin of starquakes. Of the nine firmly identified magnetars, four erupt repeatedly in bursts of X-rays and gamma rays. SGR 1806-20 is one of these so-called soft gamma repeaters.
. . "This is a rare opportunity for astrophysicists to study the interior of a neutron star, because we finally have some data theoreticians can chew on. Hopefully, they'll be able to tell us what this all means", Rothschild said.
July 13, 05: A newly discovered planet has bountiful sunshine, with not one, not two, but three suns in its sky. It is the first extrasolar planet found in a system with three stars. How a planet was born amidst these competing gravitational forces... will be a challenge for planet-formation theories.
. . The triple-star system, HD 188753, is located 149 light-years away. The primary star is like our Sun, weighing 1.06 solar masses. The other two stars form a tightly bound pair, which is separated from the primary by approximately the Sun-Saturn distance, & more or less acts as one star. The combined mass of the close pair is 1.63 solar masses. The planet's orbit centers around the main yellow star among the trio. The larger of the other two suns is orange and the smaller is red.
. . Using the 10-meter Keck I telescope in Hawaii, Konacki noticed evidence for a planet orbiting the primary star. He found a new way to identify planets by measuring velocities of all bodies in a binary or multiple star system. This newfound gas giant is slightly larger than Jupiter and whirls around its central star in a 3.5-day orbit. A planet so close to its star would be very hot. Although other so-called hot Jupiters have been found in such close-in orbits, the nearby stellar pair likely sheared off much of the planet-making material in the disk that would likely have existed around the primary star in its youth. Since this proto-planetary disk holds the construction materials for planets, there does not appear to be any safe place for any farther-off world to be assembled.
. . The typical hot Jupiter is thought to form farther out --beyond a theoretical limit called the snow line. "Past about 3 AU, it is cold enough to form ices and other solid material for building cores", Konacki said. Once a sufficiently large core is built outside the snow line, the planet can start accreting gas and --if the conditions are right-- migrate toward its sun.
. . Although this scenario appears to work in most stellar systems, it has difficulty explaining the newly-discovered planet in HD 188753. Of all the planet-harboring stars known, this is the closest that a stellar companion has ever been found. "The problem is that the pair is a massive perturber to the system", Konacki said. "Together, these two stars are more massive than the main star." Moreover, the pair goes around the primary along an oblong orbit that stretches from 6 AU out to 18 AU over a 26 year period. This eccentricity increases the instability of the disk around the primary. Konacki estimates that due to the gravitational perturbations from the pair, the proto-planetary disk was truncated down to 1.3 AU, far within the snow line. "How that planet formed in such a complicated setting is very puzzling.
. . About 30 extrasolar planets have been found around double-star systems, or binaries. This is a small percentage of the total number of extrasolar planets, even though multi-star systems outnumber single star systems. The reason for this disparity is that the main technique for locating planets --the radial velocity method-- is not well-suited for finding planets with more than one star.
. . The fact that a planet can even exist in a multiple-star system is amazing in itself. Binary and multiple stars are quite common in the solar neighborhood, and in fact outnumber single stars by some 20%.
July 13, 05: Kornreich and his student Bryant Gipson have figured out how images of landscapes and planets would be distorted by having a black hole sitting in the foreground. Such mathematical calculations have been done before for stationary black holes, but this is the first time it has been done for spinning black holes. Most black holes in the universe are thought to be rotating --many at high speeds. In a stellar black hole, which forms when a giant star dies explosively, the rotation is a logical remnant of the star's spin. Just as a skater speeds up when she pulls her arms in, the dead star's rotation picks up dramatically as remaining material collapses into a small, dense black hole.
. . The computations for a rotating black hole are complicated by the fact that space around the hole is forced to rotate with it. This so-called frame dragging will affect everything in the vicinity of the spinning black hole. "Even light rays will get pulled along with the rotation", Kornreich said. "Those that run counter to the rotation sometimes don't make it --they get sent backwards." Because some light rays are shot back at you, it is possible to see your own reflection if you look carefully at the side of the black hole rotating towards you, the thinking goes. But this does not mean astronomers will be able to see themselves through a telescope. To observe these distortions, one would have to be within about three or four times the black hole's Schwarzschild radius, said Kornreich. For a non-spinning black hole, this radius defines the event horizon --the sphere of gravitational no return. A black hole packing the mass of our Sun would have a Schwarzschild radius just 3 km. One with the Earth's mass would have a radius of about 9 mm.
. . There is a theoretical limit to the rotation speed --technically, the angular momentum-- of a black hole. Spinning faster than this limit, the event horizon disappears, exposing the point of infinite density --called the singularity-- at the center of the hole.
. . "A 'naked' singularity is a black hole that is rotating so fast that light can escape from it along certain trajectories. Hence, an outside observer could 'see' the singularity at the center", Kornreich said. A body spinning above the theoretical limit would likely fall apart before ever forming a black hole, so naked singularities are unlikely to exist. "But they are interesting to think about."
. . He explained that --rather paradoxically-- a small black hole is more deadly than a big one. "Tidal forces are worse around a black hole of lesser mass. The gravity around a small black hole is changing rapidly and that is what kills you --it stretches you into a string of spaghetti." The process is called spaghettification.
July 6, 05: The idea of dispatching a dedicated robotic probe on an interstellar trek has been seriously advocated for nearly 30 years. A recently finished appraisal of how to build such a craft shows that it is within reach --but nonetheless remains a challenging task.
. . A NASA-sponsored study team has blueprinted an Innovative Interstellar Explorer (IIE). Goal of the IIE would be to plunge outward some 200 Astronomical Units. "I think we're converging on something that's doable", said Ralph McNutt, the principal investigator for the Innovative Interstellar Explorer study. If launched in 2014, the probe would arrive at the 200 AU distance in about 2044.
. . McNutt said the relatively small spacecraft would use radioisotope power sources that energize small electric thrusters. "You need to make a spacecraft that is 'massless' as possible", he said, something akin to "unobtanium". Efficient, lightweight electric propulsion and power systems are part of the key. The Innovative Interstellar Explorer would carry a compact science payload weighing all of 30 kg. It would be boosted from Earth atop a Delta 4 heavy launcher. A custom upper stage is also required.
. . That initial launch energy in 2014 would push IIE to an arrival at Jupiter two years later where the probe would acquire a gravity assist from the massive planet. Long-term, low-thrust, continuous acceleration of the probe would be provided by a kilowatt-class ion thruster running off electricity provided by advanced Stirling radioisotope generators.
. . The interstellar probe would cruise out of the solar system at about 7.8 AU per year. It would accelerate to a "burnout" speed of 9.5 AU per year at 103 AU in November 2029. In contrast, Voyager 1 is speeding about 3.6 AU per year. Its twin, Voyager 2, is a slow poke at about 3.3 AU per year. The Voyager probes are expected to go dead around 2025 as their plutonium-fueled generators are fully discharged.
July 1, 05: A strange newfound planet as massive as Saturn appears to have the largest solid core known, providing an important clue to how some giant planets might form and setting off a controversy over how it formed.
. . The world passes in front of its host star, so even though they can't actually see it, astronomers were able to glean important information about its size and density, and therefore infer things about its composition. They say it supports the idea that giant planets can indeed form by gradual accumulation of a core, long the leading theory of planet formation but one that has been called into question lately.
. . It is very close to the star, taking just 2.87 days to make a yearly orbit. That makes it hot -- about 2,000 degrees Fahrenheit on the star-facing side. Modeling of the planet's structure shows it has a solid core approximately 70 times Earth's mass.
. . The scientists don't believe the core could have formed by cloud collapse. They think it must have grown by accumulation of dust and rock, and then acquired gas.
"I suspect that both disk instability and core accretion can occur, as well as intermediate, hybrid mechanisms", Boss said. He's a theorist at the Carnegie Institution of Washington who has championed the collapse model in recent years.
A white dwarf star weighs from ten thousand to one billion grams (1000 tons) per cubic centimeter —-depending on whether the dwarf is a youngster or an old star.
June 24, 05: Scientists have long known that hydrogen is the most abundant element in the universe. Sky watchers can easily spot it in cosmic dust clouds where it sometimes collapses to form new stars and planets. But why and how so much hydrogen is kicking around in its molecular form –-where two atoms are stuck together-– instead of in its simple single atom form has stumped scientists. Researchers at Ohio State University think they have found the key –-bumpy space dust.
. . The coldness of space makes it difficult for two hydrogen atoms to join on their own. However, put two of them next to each other on a surface and the reaction can take place, says Eric Herbst of OSU. But when Herbst and his colleagues tried to simulate the reaction in the lab, they weren't able to do it. It turns out their dust particles were too flat. When bonding hydrogen atoms, the best surface for doing this is "less like the flatness of Ohio and more like a Manhattan skyline."
June 20, 05: Astronomers discovered X-ray flashes (XRFs) in 2000. They typically last less than a minute and apparently originate in distant galaxies—traits that also belong to gamma ray bursts (GRBs), the biggest blasts in the sky. Not believing in coincidence, many scientists suspect XRFs and GRBs are part of the same family of events. If so, then XRFs are the little brothers of GRBs. They peak in X-rays, which are a factor of 100 lower in energy than the gamma rays of GRBs. The XRFs are also typically 100 times fainter than GRBs.
. . If XRFs are related to gamma ray bursts, one might wonder why they are not called X-ray bursts. Unfortunately, that name was already taken. "X-ray bursts" happen in binary systems, where one companion is stealing material from a nearby star. At times, this matter accretion speeds up, causing a brief eruption in X-rays.
. . The currently favored model for GRBs is that they originate from the death of a massive star. The star's central spinning core collapses—likely becoming a black hole—while the outer layers of the star explode in what is called a supernova. In addition, theorists suspect that—with so much matter spiraling into the core—some of the material gets sprayed out in jets that poke out of the two poles. These intense beams of fast-moving particles generate gamma ray radiation. If the Earth lies "downwind" of one of these jets, we see the event as a GRB.
. . One idea is that all supernova jets look the same, but they become less intense as you look at them at a slight angle. Seen straight on, a jet looks like a GRB, but rotate 20 or 30 degrees and it appears to be an XRF. Rotate further, and all we see is the supernova explosion.
. . According to Lamb, this "universal jet" hypothesis predicts a particular spread in GRB and XRF energies, which has not been seen. "You can try to accommodate the GRBs, but then you cannot accommodate the XRFs, or vice versa", Lamb said. In his "variable opening angle" scenario, a narrow jet—say 10 degrees across—would be a GRB, while a broad jet—maybe 40 degrees wide—would be an XRF. Lamb thinks that the focus of the jet could depend on how fast the collapsing core rotates. But he calls this a "story" -—not qualifying as a theory just yet.
June 13, 05: Astronomers have detected the smallest extrasolar planet yet: a world about seven and a half times as massive as Earth orbiting a star much like ours.
. . All of the 150 or so exoplanets found orbiting normal stars are larger than Uranus, itself 15 times Earth's mass. The new find may be the first rocky world found around a star like Sol. The newly discovered "super-Earth" orbits the star Gliese 876, located 15 light-years away --about one-third Sol's mass. This star also has two larger, Jupiter-size planets orbiting it.
. . The new planet whips around the star in a mere two days, and is so close to the star's surface that its temperature probably tops 200 - 400 Celsius (400 - 750 degrees F) --oven-like temperatures far too hot for life as we know it.
. . The planet was discovered using the so-called "wobble" technique. The researchers have measured a minimum mass for the planet of 5.9 Earth masses. It orbits Gliese 876 with a period of 1.94 days at a distance of 0.021 astronomical units (AU), or 3.2 million km.
June 13, 05: There are galaxies that inhabit the nearly empty deserts of space. Unexpectedly, these "void galaxies" are still forming hot, blue stars --even more than the average galaxy in the more populated regions of the universe. The voids are typically 100 million light-years across, and yet they contain only a few galaxies each. Taken together, the voids fill 40% of the volume of the universe, but their galaxies account for less than 5% of all galaxies.
. . The researchers found that these galaxies tend to form near the edges, as opposed to the centers, of the voids --like hermits that want to remain within earshot of civilization. But the most remarkable finding is how blue the void galaxies appear --indicating that they are still busy making stars.
. . Young massive stars burn hotter and therefore bluer. Over time, these bright blue stars use up their fuel and disappear, leaving only the less massive red stars to light up an old galaxy. The implied star formation rate in the voids is higher than what is found in the average dense environment. This was not expected, since the gas supply for making stars is thought to be gravitationally swept up by higher density regions. Most theories, therefore, assume that voids would need to form galaxies early on before the gas went away.
June 6, 05: Two dense stars whipping around each other at breakneck speed may be the strongest known source of Einstein's space-trembling gravity waves. The double star –-called RX J0806-– was discovered in 1994 in X-rays. Later shown to be blinking on and off every 5.4 minutes, the two-star setup is believed to be a pair of white dwarfs –-the dense ashes of burnt-out stars-– rotating around each other. They'll merge between 500,000 and one million years from now. That event, theory says, would unleash a colossal burst of gravitational waves.
. . The implied separation is just 75,000 km –-a mere one-fifth the distance between the Earth and the Moon, making this the closest stellar pair ever observed. The tangled duo should be booming out gravity waves –-undulations in the fabric of space and time predicted by Einstein's theory of general relativity. "Those waves have still not been detected directly, but there is indirect evidence", said Tod Strohmayer.
. . The time between the X-ray blips is decreasing by 1.2 milliseconds every year. The implication is that the dwarfs are orbiting faster and faster, as they gradually fall into each other at a rate of one inch per hour. This "spin-up" is consistent with rotational energy being lost to gravity waves. The amount of energy radiated in gravity waves in all directions could be 100 times the energy our Sun puts out in light.
. . LISA, scheduled for 2012 launch, will involve three satellites orbiting 5 million km) apart in a triangle formation. As gravity waves –-traveling at the speed of light-– wash up on the Earth's shores, the satellites can detect a change in their separation far less than the width of an atom. Relative to each other, the LISA satellites will bob one quadrillionth of a meter (roughly the size of an atomic nucleus) every 160 seconds in the J0806 surf.
June 2, 05: Frank Drake --Director, Center for the Study of Life in the Universe & Chairman Emeritus SETI Institute Board of Trustees.
. . We see a sort of greenhouse, actually made by a many-[km-thick] layer of ice, on the satellite Europa of Jupiter, so far from the Sun that the brightness of sunlight is only a few percent of that on Earth. But there is liquid water there, and a lot of it - much more than in all the oceans of Earth combined. Could there be life in this giant ocean? Our scientists are exploring this possibility, both in theory and in the planning of missions to Europa to search for signs of life.
. . The planets of dim red dwarf stars, also called M stars, are a new and exciting possibility. Long neglected as targets for SETI searches, they comprise 80% of the stars in our galaxy. Yet their starlight is so faint that only planets in close orbits would be warmed. But what warming this would be! In orbits so small, planets would be tidally locked, with the same side continually facing the star, like the near side of our Moon always faces Earth. The center of the sunny side of the planet could be scorching. The dark side would be a frozen wasteland. But, somewhere between these extreme environments, conditions might be just right for life. Perhaps on these planets there is a "Camelot" zone, just right for life, which makes planets like ours seem like the slums of the Galaxy in comparison. What might life be like in a place where the weather hardly changes, and the "sun" never sets?
. . Perhaps most provocative of all are a class of planets which must exist, but which we have never seen. These are the planets which have been ejected from their systems during the turmoil which accompanies the birth of a planetary system. These "rogues" are destined to wander through space alone, cosmic nomads, with only the light of distant stars falling on them. Shouldn't life be impossible there? Maybe not. Just as the outer giant planets of our system are warm in their interiors due to radioactive decay and other sources of energy, so the rogues could well have a deep enough atmosphere, and greenhouse effect, that they can provide a long-lived habitat for life. How strange that life must be, if it exists!
. . In our "Life in the Universe Center", the Institute is conducting perhaps the broadest program of any institution addressing the origins and nature of life in the universe. In so doing, we hope to contribute to the understanding of some of the oldest and most profound questions of science and philosophy.
May 31, 05: The Carina Nebula is a stellar nursery --a cloud of gas and dust that is 200 light-years in diameter. Located in the southern part of our galaxy, Carina is 10,000 light-years from Earth.
. . Eta Carinae, a variable star that puts out more energy than one million suns. It is sometimes touted as the stellar heavyweight champ --with a mass estimated at over 100 solar masses. Winds blow off Eta Carinae's surface at 6 million kph. During a spectacular event in the 1840s, the star shed the equivalent of 10 solar masses from its outer layers. For several years after this sloughing off, Eta Carinae was the second brightest star in the sky.
. . There have been several other eruptions in the star's past --leaving astronomers to suspect that this powder keg will go supernova sometime in the next thousand years. The ultraviolet radiation and wind from Eta Carinae and its fellow massive stars has pushed gas and dust out "like a snowplow," explained Smith. At the edge of the cleared cavity, material piled up, and eventually formed knots where new stars could form.
. . "We think the Solar system formed in one of these [nebula] environments."
May 30, 05: New measurements suggest that the nearest galaxy to our own Milky Way --Andromeda-- is three times broader than astronomers had thought. [If only slightly heavier.] They now believe a thin sprinkling of stars once thought to be a halo is in fact part of Andromeda's main disk. That makes the spiral galaxy, so close to Earth that it appeared as a fuzzy blob to the ancients, more than 220,000 light-years across --triple the previous estimate. Andromeda is 2 million light-years from Earth.
. . It appears that the outer fringes of the disk were made when smaller galaxies slammed together. The structure is too bumpy to have been formed otherwise, said Rodrigo Ibata. "This giant disk discovery will be very hard to reconcile with computer simulations of forming galaxies. You just don't get giant rotating disks from the accretion of small galaxy fragments", Ibata said.
May 30, 05: There have been many theories to explain GRBs (gamma ray bursts). The two main contenders are that GRBs arise when a massive star blows itself apart, or, alternatively, when the ultra-dense remnants of dead stars collide with each other. Two recent observations –-one of an X-ray glow following a burst and another of jets blowing out of a dying star-– appear to let GRB theorists have their cake and eat it too. That is, there may be room in the GRB world for both stellar explosions and mergers. The findings support a realization that has grown in recent years suggesting the bursts have at least two origins: the result of a merger between two neutron stars; two black holes; or a combination of the two.
. . These strange objects are the tightly-sealed coffins of long-dead stars. Smashing two of them together would unleash a great deal of energy, but there would be very little surrounding gas or dust, which is thought to fuel the long afterglow of other GRBs.
. . A second result provides verification for a very different mechanism for making GRBs. The so-called collapsar model blames GRBs on the explosion –-or supernova-– of a massive star. This stellar swan song is presumably initiated by the collapse of the star's inner core into a black hole. The model assumes that the collapse happens non-spherically –-in which case, the core squeezes down like a pancake, while beams of matter blow out of the top and bottom. The beams, or jets, emit copious amounts of gamma rays, thereby generating a GRB.
. . The collapsar model may require not only an asymmetric collapse "so that there is a natural axis along which matter can more easily squirt," but also a thin outer envelope "so that the jet doesn't have to pummel through a lot of material." Type Ic supernovae may fit the bill, since the dying star in this case has lost its hydrogen and helium envelope due to a strong out-flowing wind or a greedy stellar companion.
May 23, 05: An international team of professional and amateur astronomers has detected a massive planet circling a star some 15,000 light-years away from Earth. Using a method called gravitational microlensing, astronomers not only found the planet, but determined its size –-about three times the mass of Jupiter. Microlensing observes the brightening of distant stars by the gravitational effects from massive objects passing in front of them from Earth’s vantage point.
Small and medium sized stars are born through a collapse of gas, followed by a gradual accretion of matter through a stellar disk. But once a star reaches about 8 solar masses, its radiation is thought to blow away any remaining material - cutting off the gas supply. One theory states that stellar behemoths are built out of the collision of two medium-sized stars.
May 23, 05: In a reversal of roles, a planet has gravitationally bullied its star to rotate in step with the planet's orbit. The star's behavior is similar to that of Luna, which turns just fast enough to keep one face always pointing at the Earth.
It is unusual, however, to see the larger body --in this case a star 1.4 times the mass of the Sun-- being tidally locked by a smaller body. The planet's mass to between 7 and 8 times the mass of Jupiter.
. . Tau Bootis ("tau Boo" for short) is a star 50 light years away with a planet in a tight, 3.3-day orbit around it.
. . Although it is suspected that many of the close-in exoplanets --so-called "hot Jupiters"-- are tidally locked to their stars, this is the first detection.
. . MOST is Canada's only space telescope. Weighing a mere 132 pounds, it is relatively small as these things go. MOST was designed to see changes of a part per million in the brightness of stars. According to Matthews, this is equivalent to standing outside the Empire State Building with all its lights on and noticing when someone pulls down one window shade by 1.5 cm.
. . Moreover, with follow-up measurements of tau Boo, astronomers should be able to extract a signal from starlight bouncing off the planet. The light that reflects off a planet can tell astronomers the chemical composition of its atmosphere and whether or not this distant world has clouds.
. . Because of tidal friction, almost all systems eventually become synchronized. "Given long enough, the Earth will face the Moon", noted Cameron. The time for synchronization is faster the closer and heavier the synchronizer is in comparison to the synchronizee. Most stars do not live long enough to become locked to their planets. In the case of tau Boo, the planet weighs about 0.5% that of its star - compared to Jupiter, which is 0.1% the mass of Sol. But more importantly, tau Boo b is 100 times closer in than Jupiter is.
May 19, 05: A small prototype array in Germany has detected several radio flashes from cosmic rays that smack into the Earth's upper atmosphere. A larger array, with more of these low-cost radio antennas, could help astrophysicists decipher the mystery behind the highest energy cosmic rays.
. . Cosmic rays are high-speed sub-atomic particles --mostly nuclei and protons-- that zip around space in all directions. Lucky for us, they cannot plow very far into our atmosphere before they collide with a gas molecule. From these collisions come showers of secondary particles --including electrons, anti-electrons (called positrons), and muons, which are like heavy electrons. Cosmic rays can be characterized by the showers they produce.
. . Surprisingly, some of these space-faring projectiles have a 100 million times more energy than is possible in man-made accelerators. There are no "cosmic accelerators" in our galactic neighborhood that seem powerful enough to generate particles with this much energy.
. . Therefore, these so-called ultra-high energy cosmic rays (UHECRs) presumably come from colliding galaxies or large black holes hundreds of millions of light years away. But that raises a problem: cosmic "stuff" along the way will slow --or even outright destroy - high-energy particles traveling these great distances.
May 19, 05: Astronomers have discovered one of the closest stars to our Sun, and they say that more undetected close neighbors may be lurking in our vicinity. It is the closest star system to us after the Alpha Centauri system and Barnard's star. It ranks as the third closest star system and the fifth closest star to our Sun. It is a faint red star, a so-called red dwarf, and is only 7.5 light years away.
. . The new star was found because its relatively swift motion across the sky was picked up by automated sky surveys.
May 17, 05: Planets that revolve around two suns --or one of a pair. A theoretical investigation has explored the likelihood for worlds like this to exist. That's because more than half of the stars in our galaxy have a stellar companion. And yet, of the 130 or so currently known exoplanets (none of which are Earth-like), only about 20 of them are around so-called binaries. The percentage may grow higher. The current ratio is affected by an observational bias: planet hunters tend to avoid binaries because the star-star interactions can hide the planet signatures.
. . But planets may be just as likely around binaries as around single stars. Recent numerical simulations have shown that Earth-like planets, known as terrestrials, form readily in double star systems.
. . Wide binaries are those in which the two stars are separated by several astronomical units (AU), which is the distance between the Sun and the Earth. Planets could orbit around one of the pair, or each separately. So far, all the stellar binaries with exoplanets are wide binaries.
. . But close binaries, where the stars are less than about an AU apart, can potentially have planets in orbit around both stars. These planets, however, will be much harder to detect.
. . The researchers used computer models that start with 14 large planet "embryos" and 140 smaller planetesimals in orbit around one star or both stars of a binary. Evolution of this material is influenced by gravity and collisions. The models are followed for the equivalent of about one billion years. "All of our simulations have been able to form terrestrial planets." The simulation results can inform observers which binaries might be better targets for their telescopes.
. . For wide binaries, Earth-like planets formed as long as the two stars came no closer than 7 AU. Quintana said that about 50% of known binaries meet this constraint.
. . The research group also ran simulations that mimicked Alpha Centauri --the nearest binary system to Earth, where the closest the two stars come is about 11 AU. The secondary star apparently acts like Jupiter does in our solar system --limiting how far out planets can form. The results showed several terrestrial planets were possible around either of the stars. Planets have not yet been seen in the Alpha Centauri system, but small mass planets cannot yet be ruled out.
. . For close binaries, if the two stars are about 0.1 AU apart, the planets that form are indistinguishable from those seen in simulations with only one star. But as this separation increases, or the orbit becomes highly non-circular, it is harder for Earth-like planets to exist. "Perturbations from the stellar motions can eject matter into space or into one of the stars."
. . It will not be easy to see a planet around a binary, especially those where the stars are close to each other. Most planets have been found by the radial velocity technique that searches for Doppler shifts in the light spectra of stars. But there are situations where a binary could provide an advantage for detecting planets. If the two stars eclipse each other, a planet could change when this eclipse happens. "If the timing of the eclipses is not [exactly] periodic, maybe a planet is to blame."
May 11, 05: Young stars' violent flare-ups might actually help infant planets survive, especially rocky worlds like Earth, scientists reported. To find this out, astronomers used the Chandra X-Ray Observatory to take a 13-day unblinking look at a clump of young stars known as the Orion Nebula Cluster. The long observation allowed them to examine Sun-like stars at an early stage of their development, when they were between 1 million and 10 million years old --mere babies compared to our 4.6 billion-year-old sun.
. .The scientists discovered that these hot-headed young stars were flinging off powerful X-ray flares at an exponentially higher and stronger rate than our older, calmer sun does. As stars like our sun age, the number, size and energy of their flare-ups decrease. It would be very dangerous now for Earth to encounter the kind of massive X-ray flares that the sun may have emitted in its early life.
. . This release of energy may have ruffled the discs of dust that accumulate around young stars. These discs hold the raw material for planets, and if any infant planets had been hiding in the encircling dust, the turbulence in the disk might have prevented them from being sucked in toward the star and destroyed.
. . Half the stars in Orion showed evidence for disks, places where rocky planets might be formed. Recent studies have shown that when X-ray flares strike planet-forming disks, they interact with the disk and affect the position of a planet from a star. The astronomers theorized that energetic flares prevent developing planets from falling into the newborn star.
. . Solar flares are strong releases of energy that send protons, X-rays, electrons and other radiation streaming outward. In our solar system, such flares can sometimes cause magnetic storms on Earth by disrupting the Earth's magnetic field.
. . The Chandra telescope was carried into orbit by the space shuttle Columbia in 1999.
May 10, 05: Of the more than 140 planets found around distant stars, a large number have highly elliptical orbits, crazy oblong shapes that have surprised theorists who try to explain the configurations with near collisions or perturbing disks of gas. "This is surprising because massive planets would form in nearly circular orbits, and interactions with a gas disk would tend to keep the eccentricity low."
. . An elliptic orbit is characterized by the eccentricity, which is how much a planet's distance from its star varies as it carves out an orbit. Most of the planets in the Solar system have relatively low eccentricities, less than about 5% (tiny Pluto is not really a planet). By contrast, the average eccentricity of extrasolar planets is about 25%. And these are not Plutos. They are typically more massive than Jupiter.
Some have eccentricities of 80% [almost perpendicular!] which is as high as the crazy orbits of some comets in the solar system.
. . So the Solar system is more the exception than the rule.
. . In most cases, it is believed that the gas disk will circularize the orbit of a planet. But at some point between one million and 10 million years after the star was born, the gas disk disappears – either accreted onto the star and planets, or blown out into space. With no gas, the orbits would presumably be free to de-circularize.
. . The smaller mass planet will often get tossed out into space, while the lager planet survives in a highly elliptical orbit. Earth-sized planets usually lose out in these interactions. There are theories that our solar system started out with more planets, but some were ejected through interactions.
. . It may be possible to detect a free-floating planet –-one that got kicked out of a stellar system by a bigger bully. Previous searches for these "orphans" have come up empty. But Bennett, who looks for the gravitational magnification of background stars by foreground planets, thought this microlensing technique might get lucky and catch one of these stray planets.
. . Curiously, the more massive planets are more eccentric.
May 9, 05: Astronomers photographed a cosmic event which they believe is the birth of a black hole. A faint visible-light flash moments after a high-energy gamma-ray burst likely heralds the merger of two dense neutron stars to create a relatively low-mass black hole. The merger occurred 2.2 billion light-years away, so it actually took place 2.2 billion years ago and the light just reached Earth.
. . Gamma rays are the most energetic form of radiation on the electromagnetic spectrum, which also includes X-rays, light and radio waves.
. . It was detected by NASA's orbiting Swift telescope. Swift automatically repositioned itself within 50 seconds to image the same patch of sky in X-rays. It just barely caught an X-ray afterglow; large observatories then tracked to the location and spotted a faint visible-light afterglow. Until now, no optical afterglows from these bursts have been detected. Theorists think a burst like this represents the formation of a black hole a few times the mass of the Sun, but if so, then there should be flashes of X-rays and visible light, too.
. . Over a long time period, at least a hundred million years and perhaps billions of years, the two neutron stars spiraled toward each other. "A fraction of a second before contact, the lower mass neutron star is disrupted and forms a neutrino driven accretion disk around the higher mass neutron star. It implodes under the weight and forms a maximally spinning low-mass black hole."
. . Each burst can briefly outshine an entire galaxy. Gamma-ray bursts in our own galaxy are very rare. Some scientists speculate that such bursts in the Milky Way's past might have caused mass extinctions on Earth.
May 9, 05: Marcy predicts that the frequency of gas giants on long orbits is as high as those closer in. If correct, then about 12% of normal stars have at least one Jupiter or Saturn.
. . Livio gave a star-forming region, where the radiation is so high that it may blow out most of the gas around the young stars. The cores, however, would presumably survive to form smaller planets like Earth. "I imagine most stars have terrestrial planets. It seems hard *not to form them."
. . Detection sensitivities in the radial velocity technique have improved to the point that a few Neptune-sized planets --around 20 times the mass of the Earth-- have now been spotted. But it will be hard to see planets of much lower mass with radial velocities. They simply do not tug on their stars hard enough. Fortunately, another planet detection scheme, which relies on a planet blocking or brightening the light from a star, may take up the slack.
. . To date, seven planets --all large and close-in-- have been found by this transiting method. Careful follow-up observations of transits have detected planetary atmospheres and - just last month - the Spitzer Space Telescope observed the heat-radiation from two transiting planets, which implied they were around 1,500 degrees F.
. . The other way a planet affects starlight is by gravitationally magnifying the light from a distant star. This is similar in concept to the lensing by galaxies, but it is a much smaller effect - hence the name: microlensing. Here's how it works:
. . Stars can magnify other stars in our galaxy when one passes in front of the other, owing to the fact that the gravity of an object bends light coming from a more distant object. If the lensing star has a planet around it, the magnification can be greater. One advantage of microlensing is that it is more sensitive to large planet-star separations.
. . Although both microlensing and transiting are relatively new to the planet-hunting game, they may be the best chance of detecting an Earth-sized planet outside our solar system. A future space mission using the transiting method, called Kepler, is specifically designed to ferret out Earth-sized planets, largely within one AU of their host stars. "We expect to see thousands of terrestrial planets, if they are common", said Bill Borucki, the principal investigator for Kepler. "Even if they are rare, we should see a few hundred." Kepler is currently scheduled for a June 2008 launch.
May 9, 05: "The capability of seeing, detecting, planets the size of the Earth is only now just coming into our grasp", said Jaymie Matthews, an astronomer at the University of British Columbia. "I think we can look forward reasonably in the next decade to finding out are there Earth-size planets in Earth-like orbits going around every star", said Tim Brown of the National Center for Atmospheric Research. "We're going to have to wait a while to find out whether they have atmospheres."
. . As of now, about 6% of normal stars surveyed have a gas giant planet. Most of these planets are very close to their star - some with orbital periods, or "years", as short as a few days. Such tight orbits creating scorching conditions. This preponderance of big, close-in planets --so-called hot Jupiters-- has developed because the early years of planet-hunting have been dominated by the radial velocity method, which relies on detecting a wobble in the host star due to the gravitational tug from the orbiting planet. The tug is bigger when the planet is closer and larger, and so hot Jupiters are easiest to find.
May 7, 05: The Big Bang could be a normal event in the natural evolution of the universe, & one that will happen repeatedly over incredibly vast time scales as the universe expands, empties out and cools off, say Carroll and graduate student Jennifer Chen. It could've arisen from an energy fluctuation in empty space that conforms to the known laws of physics.
. . Other researchers have long suggested that the universe is cyclic, and that the Big Bang was the beginning of our universe as we know it, but not the beginning of the larger Universe that encompasses everything, including that which we can never see because it's beyond our cosmic bubble.
. . Carroll and Chen argue that a generic initial condition is actually likely to resemble cold, empty space —0not an obviously favorable starting point for the onset of inflation.
. . In a universe of finite entropy, some scientists have proposed that a random fluctuation could trigger inflation. This, however, would require the molecules of the universe to fluctuate from a high-entropy state into one of low entropy — a statistical long shot.
. . "The conditions necessary for inflation are not that easy to start", Carroll said. "There's an argument that it's easier just to have our universe appear from a random fluctuation than to have inflation begin from a random fluctuation."
. . But even empty space has faint traces of energy that fluctuate on the subatomic scale. As suggested previously by Jaume Garriga of Universitat Autonoma de Barcelona and Alexander Vilenkin of Tufts University, these fluctuations can generate their own big bangs in tiny areas of the universe, widely separated in time and space. Carroll and Chen extend this idea in dramatic fashion, suggesting that inflation could start "in reverse" in the distant past of our universe, so that time could appear to run backwards (from our perspective) to observers far in our past.
. . Regardless of the direction they run in, the new universes created in these big bangs will continue the process of increasing entropy. In this never-ending cycle, the universe never achieves equilibrium. If it did achieve equilibrium, nothing would ever happen. There would be no arrow of time.
Apr 30, 05: New images taken of an object five times the mass of Jupiter confirm that it is a giant planet closely orbiting a brown dwarf, known as 2M1207A, at a distance nearly twice as far as Neptune is from Sol. The distance is 55 times as great as that between the Earth and its sun [ie 55AU]... but the actual orbit radius could be twice that depending on whether the planet-like object orbits in a circle or not. In comparison, Neptune orbits at about 30 AU. The brown dwarf and its companion have, respectively, 25 and 5 times the mass of Jupiter. The ratio of five to one is surprising: most of the planets found so far have a mass ratio of about 1000 to one.
. . Earlier this month, German astronomers published a photograph of an object 450 light-years from Earth that they claimed was the first direct image of an extrasolar planet. But astronomers sparred over the photo, saying that it was possible that it could be a brown dwarf based on the object's mass.
. . Last month, scientists using NASA's Spitzer Space Telescope said they directly measured light from two known Jupiter-sized gas planets orbiting distant stars, but did not get images of the planets separate from their stars.
. .
Jill Tarter --Director of the Center for SETI Research:
. . "Statistically, it is extremely unlikely that our fist contact with an ETI civilization will also be its first contact with an ETI civilization. Thus the advanced technology we detect will have experienced this type of encounter many times before. It already may have established a galactic protocol for information interchange, to which ab initio transmissions by Earth will have no chance of adhering. Thus we justify our asymmetrical listen-only strategy.
. . Sitting in the midst of our own exponential increase in technological capability, we cannot imagine what an older technology might look like. Thus far, we’ve never experienced any exponential growth in nature or culture that does not reach some resource limit and saturate, or crash. Some futurists speculate about the ‘singularity’ that must occur when change takes place on timescales that are too short for humans to adapt, and the post-biological entities that might evolve to accommodate the exponential –-or not.
Apr 20, 05: Astronomers have found evidence for an asteroid belt around another star similar to our Sun. Asteroid collisions create lots of dust. NASA's Spitzer Space Telescope was used to spot a thick swarm of dust around a star called HD 69830, 41 light-years away. The scientists believe the dust represents a belt of asteroids in which major collisions occur every 1,000 years or so. "Because this belt has more asteroids than ours, collisions are larger and more frequent, which is why Spitzer could detect the belt."
. . HD 69830's belt contains about 25 times more material. If there's a planet around the star, its night sky would be graced by a band of light, similar to but 1,000 times brighter than the Zodiacal Light seen from Earth. "The night sky would be quite spectacular."
In several billion years, the group of which our galaxy is a member will be torn apart as it merges with the nearby Virgo cluster.
Apr 11, 05: A new generation of ground-based telescopes could be up to 10 times the size of existing instruments and have vision 40 times as sharp as the Hubble space telescope. Astronomers have been hailing the plans, as a European project to build an Extremely Large Telescope (ELT) enters a design testing phase. ELTs would incorporate adaptive optics, a computer controlled system that deforms the mirror to adjust for the atmospheric turbulence that distorts light waves coming into the telescope.
. . One of the most exciting areas in which ELTs are certain to have a major impact is the search for Earth-like planets and by extension extra-terrestrial life. Astronomers have already detected about 150 planets orbiting other stars. ELTs could study the chemical composition of Earth-like planets, detecting the presence of liquid water, oxygen or methane. Telescopes this powerful might even be able to detect vegetation on a distant planet, by looking at a characteristic spectral signature from chlorophyll, the key pigment involved in photosynthesis.
. . Some ELT designs involve combining several circular 8m-wide mirrors. But others, like the Owl and the Euro-50, will have mirrors constructed from many small hexagonal segments.
. . The European Southern Observatory's Owl concept could be by far the largest telescope ever built, with a spherical primary mirror that could stretch up to 100m across. The Owl design uses a spherical, rather than the usual parabolic, mirror shape to cut down on cost. This means its segments can be the same shape and size and can be mass-produced. But this also means the telescope's field does not have a focus, so the Owl requires several corrective mirrors. The Owl concept works for a telescope of around 100m, but below the 60m mark, the Euro-50 design --with its smaller parabolic mirror-- may strike a better deal between cost and performance.
Apr 8, 05: Astronomers have discovered a loop-like structure some 20 light-years across close to the center of the Milky Way. And the team that found it believes the vast, bizarre structure could be some form of cosmic particle accelerator. The loop may produce sub-atomic particles with a thousand times more energy than those in man-made accelerators.
Apr 6, 05: UK and Australian astronomers are about to use a new instrument to detect the most distant galaxies yet observed. They hope to see stars that were more than 12 billion light-years away. "That takes us back 12.8 billion years and that's 650 million years after the Big Bang."
. . Dazle is tuned to search for specific infrared wavelengths of light that should be associated with some of the first stars to shine in the Universe. Dazle stands for Dark Age Redshift Lyman Explorer. The instrument must be cooled to -40 Celsius and will sit inside a large freezer box. The instrument will be fitted to the 8 meter Melipal Very Large Telescope at Paranal in Chile.
. . The research is part of the major drive in astronomy now to tie down the timings of key events in the early Universe. There is every reason to believe the technique on which it depends could get out to redshifts in the region of 15, just a little under 300 million years after the Big Bang.
. . Giant new telescopes are proposed for the next few decades. The facilities would have tremendous power, gathering light on mirrors that are 100 METERS across!
Apr 6, 05: Astronomers have seen the light coming from what could be some of the very first stars to shine in the Universe. These ancient objects burst into life probably no more than 600 million years or so after the Big Bang itself.
Apr 5, 05: Dust in the Wind... Astronomers have discovered a dusty wind that blew off a star right before it exploded into a supernova. This is the first time that a wind has been observed from this type of supernova precursor. The dust-filled gale was detected around SN 2002ic, a Type Ia supernova about a billion light years from Earth. Type Ia supernovae occur when a small compact star, called a white dwarf, gobbles up mass from a companion star. At a certain point, the mass becomes too great and the white dwarf explodes.
Apr 5, 05: New computer simulations of known extrasolar planetary systems suggest about half of them could harbor an Earth-like world, mathematically speaking. All of the known planets orbiting other Sun-like stars --there are at least 140-- are very massive, most similar in heft to Jupiter. Earth-sized planets, if any exist, can't be found with present technology --with the exception of a handful discovered around a dying star. But several models by different groups have shown rocky planets about the size of Earth could exist in known systems where a giant planet orbits a Sun-like star.
. . In the new work, researchers created hypothetical giant planets and found that each creates two disaster zones --one inside its orbit (closer to the star) and one outside. A fledgling Earth in either zone will either be lured into a collision with the larger planet, will hit the star, or will be tossed out to the cold, dead, far suburbs of the system.
. . That's no surprise. But the specifics of the model bear attention: The disaster zones are governed by the giant planet's mass and the eccentricity of its orbit, or how noncircular it is. "The larger its orbital eccentricity, the greater the gravitational reach of the giant." To allow an Earth-sized planet in a stable orbit within a habitable zone, the giant must either be well outside that zone, as Jupiter and the other giants are in our solar system, or well inside.
Apr 1, 05: Thus far, 90% of all detected alien planets have host stars that can flare and sterilize the surface of the planet. Furthermore, planets, which are that close to their host star, would be in a synchronous orbit. This means that only one side of the planet would face the host star and all potential water on that side would evaporate and go to its dark side.
Apr 1, 05: Some argue that the search for planets should not be limited to main sequence stars like our sun. The main sequence is only the first stable period of our sun's life; when it begins to burn its hydrogen around a growing helium core it offers another period of several billion years of stability. Finally, stars that have the right mass eventually become red giants; the temperature of the star's core increases as it shrinks, but the outer layers expand and cool. The "habitable zone" of a red giant (like the sun will be) extends from about 630 million miles to 2 billion miles.
. . About 150 sub-giant and red giant stars are situated within 100 light years of Earth (compared to about 1,000 main sequence stars). NASA's Terrestrial Planet Finder space mission will focus only on main sequence stars. These stars will have habitable planets that are further from their suns, and will therefore be easier to find in the glare of the parent stars.
Apr 1, 05: Astronomers have finally obtained the first photograph of a planet beyond the solar system. The planet is thought to be one to two times as massive as Jupiter. It orbits a star similar to a young version of Sol --GQ Lupi. It's very far from the star --about 100 times the distance between Earth and the Sun, another factor in helping to separate the light between the two objects.
. . The planet is only 156 times fainter than the star, because the planet is still very young and hence still forming, still contracting." [thus, still warm] The planet is about 3,140 degrees F (2000 Kelvin) --not the sort of place that would be expected to support life. Neuhaeuser's team has also detected water in the planet's atmosphere. The world is expected to be gaseous, like Jupiter. It is about twice the diameter of Jupiter. The mass estimate --one to two times that of Jupiter-- is "somewhat uncertain". Weighing it precisely would involve noting the gravitational wobble the apparent planet induces on the star, but this object is too far from the star to produce a meaningful wobble. Yet even if the object is four times the mass of Jupiter, it would still be considered a planet.
. . It's three times farther from GQ Lupi than Neptune is from Sol. "We should expect that the planet orbits around the star, but at its large separation, one orbital period [a year] is roughly 1,200 years, so that orbital motion is not yet detected." It's also possible the newfound planet has a highly elliptical orbit and is currently near its outer bounds.
. . GQ Lupi is part of a star-forming region about 400 light-years away. At 70% the mass of Sol, it is "quite similar". But GQ Lupi is only about 1 million years old. The Sun is middle-aged, at 4.6 billion years old.
. . Jayawardhana wonders whether it formed in a protoplanetary disk much closer in, roughly where Jupiter is in our solar system, and then get flung out. Or if it was born almost at the same time as its star, fragmenting out of a contracting protostellar cloud. "One way or another, this object must have formed pretty quickly" given the star's age, he said.
Mar 24, 05: The glow of planets outside our solar system have been spotted in the first direct detections of light emitted by alien worlds. The two planets were detected in infrared light, an emission of heat that is not visible to the human eye. There are no conventional photographs, but astronomers are ecstatic nonetheless.
. . One planet is known as HD 209458b, nicknamed Osiris. [There it is! I've been waiting for the first NAME for an extra-Solar planet!] It's slightly more massive than Jupiter and is about 150 light-years from Earth.
. . The gas giant worlds, each around a different star, were discovered previously by noting the gravitational wobbles they induce in their host stars -- an indirect method. Both are roughly Jupiter-sized and hot, orbiting very close to their stars. Each completes a "year" in less than four days.
. . The new technique, using NASA's Spitzer Space Telescope, allows astronomers to probe the temperatures, atmospheres and emissions of planets. It might even let them measure wind for the first time on a planet around another star.
. . TrES-1 and its star are about 500 light-years from Earth. In each system, the planet is in a direct line of sight in relation to the star, so that the planet moves across the star and then is eclipsed as it orbits around the star's back side. By comparing the total infrared emission from the reduced amount when the planet is eclipsed, Spitzer revealed the planet's exact emissions.
. . From the new detection, astronomers learned both planets are at least 1340 Fahrenheit (727 degrees Celsius) and have circular orbits. HD 209458b is arguably the most well studied extrasolar planet. Previous work by Charbonneau and others revealed oxygen and other gases in its atmosphere. It is so hot and close to its star that it is rapidly losing its atmosphere, according to another study.
. . Astronomers are still waiting for the first definite image of an extrasolar planet. The pictures may already have been taken, of a world orbiting a failed star known as a brown dwarf.
. . Those observations, by the European Southern Observatory and the Hubble Space Telescope, await confirmation. And the planet, if it is one, is unusually massive, with perhaps five times the heft of Jupiter. Imaging it --as a point of light-- was possible because brown dwarfs do not create the overwhelming glare of a normal star.
Mar 22, 05: Riotto and a team of theoretical physicists in the US and Canada say there's no need to add dark energy as a new ingredient to explain the increasing speed of universal expansion. "Our solution to the paradox posed by the accelerating universe relies on the so-called inflationary theory, born in 1981", Riotto proposed last week. According to this theory, the universe went through a period of exponential expansion in the moment immediately following the Big Bang. During this expansion, tiny ripples in space-time, much like those produced by a rock thrown in a pool, were produced. With a universe that is infinite, these ripples continue to stretch and grow with expansion and over time are causing cosmic acceleration.
. . New York University physicist Georgi Dvali sees the answer in yet another theoretical phenomenon: leaking gravity. His hypothesis relies on string theory, which states that there are extra, hidden dimensions beyond the three directions and time. In such a case, gravitons, hypothetical elementary particles transmitting gravitational forces, may escape to other dimensions. This, Dvali explained earlier this year, would cause "leaks" in gravity over cosmic proportions, reducing gravitational pull at larger distances, altering the space-time continuum and effectively speeding up universal expansion.
. . "No mysterious dark energy is required", said Antonio Riotto. "If dark energy were the size that theories predict ... it would have prevented the existence of everything we know in our cosmos. ... We think Einstein was right when he said he was wrong", said Edward W. Kolb of the U.S. Department of Energy's Fermi National Accelerator Laboratory.
. . Cosmologist Michael Turner at the University of Chicago, who coined the term "dark energy": "But they may get the last laugh. And the interesting thing is, if they get the last laugh, I doubt that this is the only effect of these long ripples. We may have to make some other changes." That could include changes to theories about the ultimate fate of the universe, particularly whether it will collapse in a "big crunch", be completely blown apart in a "big rip" or just drift steadily until galaxies are so far away from each other they cannot be seen --in effect taking stars from the sky. The ramifications of the "long ripples" proposal would be infinite drift and "cosmic darkness", Riotto said.
Mar 15, 05: The Large Magellanic Cloud, or LMC, is about 160,000 light-years away. It is considered a satellite to our Milky Way. It has a strong and ordered magnetic field, even though the field ought to be in disarray since the galaxy itself is being torn apart. Astronomers think star explosions are blowing the magnetic field into shape, something like inflating a ball. And the process, which has never been supported by clear evidence before, may be at work in all galaxies.
Mar 14, 05: New observations reveal that the early universe had its own version of rock-and-roll stars --galaxies that grew fast and died young. What killed these up-and-comers is not yet known. The galaxies, which typically had about 100 billion stars, constitute a variety of different types: some forming new stars, some clouded by dust, and some quite dead in terms of their ability to make new stars.
The most surprising are the dead galaxies that literally ran out of gas --or at least cold gas-- for making new stars. These giants suffocated far sooner than expected.
. . A plausible mechanism is that a super-massive black hole in the center of these dead galaxies is swallowing up gas and spewing out jets and radiation in a way that disrupts star formation in the rest of the galaxy.
Mar 10, 05: Stars at their birth cannot get any larger than 150 times the mass of the Earth's sun, NASA astronomers said, citing research based on data from the Hubble telescope.
Mar 3, 05: The Universe is calculated to be about 13.7 billion years old, born from a "Big Bang" --the explosion which spewed out the hot matter that later formed the galaxies and everything in them. As the light from a newly-discovered cluster has taken nine billion years to reach us, its galaxies were already formed when the Universe was a mere youth of five billion years old.
Mar 3, 05: A strange and powerful burst of radio waves from near the center of our galaxy may have come from a previously unknown type of space object, U.S. astronomers reported. Other experts nicknamed the mysterious source a "burper" and said there would be a race to scan for similar radio bursts.
. . "An image of the Galactic center, made by collecting radio waves of about 1 meter in wavelength, revealed multiple bursts from the source during a seven-hour period from Sept. 30 to Oct. 1, 2002 --five bursts in fact, and repeating at remarkably constant intervals." The burst came from the direction of the middle of the Milky Way galaxy, of which Earth is a part, and could have originated from as far away as 24,000 light-years or from as close as 300 light-years.
. . It cannot have come from a celestial object known as a pulsar, the researchers write, but the source could be a brown dwarf of a magnetar --a strange star with an extremely powerful magnetic field.
Feb 28, 05: The theory that the accelerated expansion of the universe is caused by mysterious "dark energy" is challenged by New York University physicist Georgi Dvali. He thinks there's just a gravity leak.
. . Scientists have known since the 1920s that the universe is expanding. In the late 1990s, they realized that it's expanding at an ever-increasing pace. At a loss to explain the stunning discovery, cosmologists blamed it on dark energy, a newly coined term to describe the mysterious antigravity force apparently pushing galaxies outward. This repulsive, unknown force is believed to make up more than 70% of the mass-energy budget of the universe.
. . But the existence of dark energy is far from proven, and some researchers believe they and their colleagues simply don't understand gravity at larger scales. The gravitational pull between any two objects becomes less with distance. But in Dvali's view, it weakens more than standard theory predicts. Dvali would modify the theory of gravity so that the universe becomes self-accelerating, eliminating the need for dark energy.
. . Dvali borrows from string theory, which states that there are extra, hidden dimensions beyond the four we are familiar with: three directions and time. String theory suggests that gravitons -- hypothetical elementary particles transmitting gravitational forces -- can escape to other dimensions. Dvali says this would cause "leaks" in gravity over cosmic proportions, reducing gravitational pull at larger distances more than expected.
. . The speeding up of the universe suggests that Einstein's laws of General Relativity, describing the interaction of space and matter, must be modified at large cosmic distances.
. . The idea might be testable. Gravity leakage should create minor deviations in the motion of planets and moons. Astronauts on the Apollo 11 mission installed mirrors on the lunar surface. By shooting lasers at the mirrors, a reflected beam can be monitored from Earth to measure tiny orbital fluctuations. Dvali said deviations in the Moon's path around Earth might reveal whether gravity is really leaking away.
Feb 27, 05: There’s already indirect evidence that Jupiter-sized worlds have been ejected from some of the extrasolar planetary systems we’ve discovered in the last decade. The clue is that large planets in these systems often have highly elliptical orbits. (escape velocities are 41% higher than orbital velocities.)
. . How often does this happen? "I don’t know what fraction of planets will be tossed out", Lin admits. "But I would imagine the fraction is probably pretty high; in fact I wouldn’t be surprised if it were 50%." If that’s the case, then orphan planets could be more numerous than stars! In our own galaxy alone, there would be hundreds of billions of these wandering worlds.
Feb 23, 05: Astronomers have discovered an invisible galaxy that could be the first of many that will help unravel one of the universe's greatest mysteries. The object appears to be made mostly of "dark matter", material of an unknown nature that can't be seen.
. . In the early universe, dark matter condensed like water droplets on a spider web, the thinking goes. Regular matter --mostly hydrogen gas-- was gravitationally attracted to a dark matter knot, and when the density became great enough, a star would form.
. . The theory suggests that pockets of pure dark matter ought to remain sprinkled across the cosmos. In 2001, a team led by Neil Trentham of the University of Cambridge predicted the presence of entire dark galaxies. The newfound dark galaxy was detected with radio telescopes. Similar objects could be very common or very rare. There could be more dark galaxies than ordinary ones.
. . They looked for radio-wavelength radiation coming from hydrogen gas. They found a well of it that contains a hundred million times the mass of the Sun. It is now named VIRGOHI21. The well of material rotates too quickly to be explained by the observed amount of gas. Something else must serve as gravitational glue. "From the speed it is spinning, we realized that VIRGOHI21 was a thousand times more massive than could be accounted for by the observed hydrogen atoms alone. The ratio of dark matter to regular matter is at least 500-to-1, which is higher than I would expect in an ordinary galaxy."
. . Other potential dark galaxies have been found previously, but closer observations revealed stars in the mix. Intense visible-light observations reveal no stars in VIRGOHI21. The invisible galaxy is thought to lack stars because its density is not high enough to trigger star birth.
. . The discovery was made in 2000 with the University of Manchester's Lovell Telescope, and the astronomers have worked since then to verify the work. It was announced today.
Dark matter makes up about 23% of the universe's mass-energy budget. Normal matter, the stuff of stars, planets and people, contributes just 4%. The rest of the universe is driven by an even more mysterious thing called dark energy.
. . Scientists suspect the bulk of dark matter involves tiny particles they've yet to detect. The two leading candidates are called axions and neutralinos. Whatever they are, they are known to interact gravitationally with regular matter. Dark matter particles appear not to interact with electromagnetic forces, however. They don't make or reflect light, which explains why they can't be seen.
. . Scientists at first assumed dark matter was distributed evenly in a massive halo around each galaxy. Not quite true, Ma and others have come to believe. The halos are there, but so possibly are thousands of clumps that can be thought of as dark, satellite galaxies. For every normal, star-filled galaxy, there might be 100 that contain primarily stuff we can't see.
. . Ma and Bertschinger let millions of hypothetical dark matter particles interact over billions of years in a computer model governed by gravity. Many of the particles coalesce into central clumps as massive as billions of suns, a neat fit with expectations for the process that would build a normal galaxy. But thousands of dark galaxies develop in the simulation, too, each containing masses equal to several million suns.
. . A small portion of dark matter has already been identified and is no longer mysterious. Tiny particles called neutrinos, once thought to be massless, are now known to make up a sprinkling of the total dark matter column of the budget. Cold dead stars, recently found to be plentiful, also contribute modestly to this accounting.
. . Conventional theory holds that neutrino mass does not change over time. In the new theory, neutrinos gain mass when given some room. As they move apart, a tension develops between them, like that in a stretched rubber band. The increasing tension is the infamous dark energy. The tension has been given a name: the acceleron.
. . Neutrinos create an acceleron field, much like a charged particle creates an electric field, except that this force is always attractive. The theory also predicts that neutrinos will change mass based on how densely they're surrounded by ordinary matter.
. . "In our theory, eventually the neutrinos would get too far apart and become too massive to be influenced by the effect of dark energy any more, so the acceleration of the expansion would have to stop", Nelson said. "The universe could continue to expand, but at an ever-decreasing rate."
. . Scientists are cautious about the theory.
Feb 18, 05: A huge explosion halfway across the galaxy packed so much power it briefly altered Earth's upper atmosphere in December, astronomers. No known eruption beyond our solar system has ever appeared as bright upon arrival. But you could not have seen it, unless you can top the X-ray vision of Superman: In gamma rays, the event equaled the brightness of the full Moon's reflected visible light. The blast originated about 50,000 light-years away and was detected Dec. 27.
. . The commotion was caused by a special variety of neutron star known as a magnetar. These fast-spinning, compact stellar corpses --no larger than a big city-- create intense magnetic fields that trigger explosions. The blast was 100 times more powerful than any other similar eruption witnessed. "Had this happened within 10 light-years of us, it would have severely damaged our atmosphere and possibly have triggered a mass extinction." There are no magnetars close enough to worry about, however.
The effect was similar to a solar-induced disruption but that the effect was "much smaller than a big solar flare." Still, scientists were surprised that a magnetar so far away could alter the ionosphere.
. . "This is a once-in-a-lifetime event", said Rob Fender of Southampton University in the UK. "We have observed an object only 20 kilometers across [12 miles], on the other side of our galaxy, releasing more energy in a tenth of a second than the Sun emits in 100,000 years." Some researchers have speculated that one or more known mass extinctions hundreds of millions of years ago might have been the result of a similar blast altering Earth's atmosphere. There is no firm data to support the idea, however.
. . The star, named SGR 1806-20, spins once on its axis every 7.5 seconds, and it is surrounded by a magnetic field more powerful than any other object in the universe. Millions of neutron stars fill the Milky Way galaxy. A dozen or so are ultra-magnetic neutron stars --magnetars. The magnetic field around one is about 1,000 trillion gauss, strong enough to strip information from a credit card at a distance halfway to the Moon.
Betelegeuse is near the end of its career. (yes, "beetle-juice") It is some 522 light-years away and no longer shines with a steady light. It is a "pulsating" star, expanding and contracting spasmodically with a diameter that varies from 550 to 920 times that of the Sun, but so irregular are these pulsations that no one can predict exactly when it will expand or contract.
. . In such stars, the core produces successively heavier elements to balance the incessant crush of gravity. But once the core begins creating iron, a star’s days are numbered; the formation of elements heavier than iron consumes rather than produces energy. Eventually, since the core can no longer support the star’s vast weight, it collapses, triggering a cataclysmic supernova explosion. Betelgeuse is in its final stage and could explode in only a few million years.
Feb 9, 05: The energy created when black holes merge contributes to star formation while blowing gas to the outskirts of a galaxy, this creates a limit as to how much the black hole can consume, a new computer simulation shows.
. . Black holes have a reputation for sucking in everything, but in fact they lure distant material with no more force than any other object of equal heft; a black hole's mass determines its gravitational effect. The most supermassive black holes typically contain less than 1% of the mass of a galaxy.
. . The intense radiation and fog of gas around a quasar prevents astronomers from seeing what's going on inside --it's like trying to spot the mechanism inside a glaring light bulb-- so firm conclusions about the process are difficult.
. . "We've discovered that the energy released by black holes during a quasar phase powers a strong wind that prevents material from falling into the black hole. Our results also explain for the first time why the quasar lifetime is such a short phase compared to the life of a galaxy."
Feb 8, 05: Moving at more than 670 km per second, a speedy star's path has been traced back to the galactic center. Here's what astronomers think happened: it was once part of a two-star system. Like all stars in the Milky Way, the pair orbited the center of the galaxy. But they got precariously close to the central black hole, which has a mass of more than 3 million Suns. The gravitational interaction shot the star outward.
. . "We have never before seen a star moving fast enough to completely escape the confines of our galaxy. Only the powerful gravity of a very massive black hole could propel a star with enough force." The *orbital energy of the tight-circling pair was transferred to the fleeing star too.
. . The star took about 80 million years go from the galactic center to its present location, and it is at least that old. It is moving almost directly away from the center of the galaxy. Finally, the star is laden with heavy elements, which are prevalent toward the center of the galaxy.
. . It is currently in the galactic outskirts, about 195,000 light-years from the center, and it's a similar distance from Earth. It is travelling at twice the speed needed to escape the gravitational clutches of the galaxy. About 80 million or 100 million years from now, Brown said, the star will exit the galaxy and become a lone wanderer of intergalactic space.
Feb 8, 05: NASA's infrared Spitzer Space Telescope has spotted a dusty disc of material around a very small "failed star" called a brown dwarf, raising the possibility that there may be miniature solar systems in which planets orbit objects not much larger than planets, scientists said. It's only about 15 times the mass of Jupiter, much smaller than any other brown dwarf known to be surrounded by a disc of planet-building material. Apparently no planets have developed yet, but the disk has enough material to create one small gas giant planet and a few Earth-sized, rocky worlds.
. . Brown dwarfs are star-like objects with masses less than one-tenth the mass of Sol. Although they probably formed in the same way as stars, brown dwarfs are not massive enough to ignite and don't shine.
. . This leads to all sorts of new questions, like 'Could life exist on such planets?' or 'What do you call a planet circling a planet-sized body? A moon or a planet?'
Feb 8, 05: Planet Tiffany: according to astronomer Marc Kuchner, Some planets in our galaxy could harbor an unexpected treasure: a thick layer of diamonds hiding under the surface, astronomers reported. That kind of planet would have to develop differently from Earth, Mars and Venus, so-called silicate planets made up mostly of silicon-oxygen compounds. Carbon planets might form more like some meteorites than like Earth, which is believed to have condensed from a disk of gas orbiting the sun. In gas with extra carbon or too little oxygen, carbon compounds like carbides and graphite could form instead of silicates. Any condensed graphite would change into diamond under the high pressures inside carbon planets, potentially forming diamond layers inside the planets many miles thick.
. . Carbon planets would be made mostly of carbides, although they might have iron cores and atmospheres. Carbides are a kind of ceramic used to line the cylinders of motorcycle engines, among other things.
. . Planets orbiting the pulsar PSR 1257+12 may be carbon planets, possibly forming from the disruption of a star that produced carbon as it aged. Other good candidates for carbon planets might be those located near the galaxy's center, where stars have more carbon than the sun. In fact, the galaxy as a whole is becoming richer in carbon as it gets older, raising the possibility all planets in the future may be carbon planets.
Feb 9, 05: By combining Doppler shift data from the Green Bank Telescope and other radio instruments, astronomers now know that while Titan's winds are relatively weak at the moon's surface, they reach nearly 434 km an hour at an altitude of about 120 km. At an altitude of about 59 km, Huygens found highly variable winds that may be a region of vertical wind shear.
Feb 7, 05: An object smaller than Pluto has been discovered orbiting a dying star in what astronomers said resembles a pint-sized version of the Solar system. It is 1,500 light years away. Dim solar systems may be common. They also have scientists wondering anew what really constitutes a planet and what sorts of exotic worlds might harbor life. The object, just one-fifth the size of Pluto, was called the smallest object ever found outside the Solar system.
. . The object orbits a burned out, fast-spinning neutron star known as a pulsar. Three other roughly Earth-sized planets were already known to circle the pulsar. Their orbits are similar to those of Mercury, Venus, and Earth. Though rocky, like Earth, all four objects are considered dead worlds, because the star they circle ended its normal glowing life long ago in a massive explosion.
. . The newfound small object orbits the pulsar at a distance equal to that from Sol to the "asteroid" belt, which is between the orbits of Mars and Jupiter. Observations suggest it marks the outer fringe of material that went into making the miniature solar-type system.
. . "Because our observations practically rule out a possible presence of an even more distant, massive planet or planets around the pulsar, it is quite possible that the tiny fourth planet is the largest member of a cloud of interplanetary debris at the outer edge of the pulsar's planetary system."
. . The pulsar planetary system has proved easier to probe, thanks to the central star's rapid spin and clockwork pulsation. Wobbles induced by the gravity of the orbiting objects causes slight perturbations in the pulsations. All orbit the pulsar in the same plane, just as all the planets in our solar system circle Sol in much the same plane --Pluto doesn't.
. . About the only thing astronomers can say for sure is that almost everything they find in space seems to have the potential for an orbiting companion of some sort. And, it is becoming evident that planet formation as it is thought to have happened in our solar system may occur in a similar manner in significantly different environments.
Feb 3, 05: Two monster cosmic clouds could hold the solution to the mystery of the missing matter -- immense amounts of celestial stuff that somehow has eluded detection. The big clouds of hot gas near a distant galaxy are the best evidence yet that a vast cosmic web holds all the ordinary matter that went missing some 10 billion years ago, researchers using the Chandra X-ray Observatory reported.
. . Computer simulations indicated that the missing matter might be hiding in an extremely diffuse web of gas clouds from which galaxies and clusters of galaxies formed. However, these clouds have been hard to spot because of their vast temperature range --from a few hundred thousand degrees to 1.8 million degrees F (1 million degrees C)-- and their extremely low density. This makes them a very specific sort of stuff known as warm-hot intergalactic matter, or WHIM. Evidence of WHIM had been detected around the Milky Way, which contains Earth, and in its galactic neighbors, but there was no definitive evidence.
. . Chandra managed to spot two much more distant clouds of WHIM. The clouds are so diffuse that they need a bright light behind them to make them detectable, something like car headlights illuminating fog. Huge outbursts in the galaxy emitted enough X-rays to let astronomers detect the WHIM clouds.
Feb 3, 05: Some of the universe's missing "normal" matter has been found hiding in clouds of hot gas between galaxies, according to research. Just 5% of the universe is believed to be made up of "normal" matter such as atoms and molecules, but scientists have only be able to find about half the expected amount.
. . They looked at X-rays from a distant quasar called Markarian 421 as they passed through a region of warm gas. The X-rays were absorbed by ionized oxygen and nitrogen atoms there that are normally "invisible", and the scientists say there is enough matter in the gas to account for the missing mass.
Feb 1, 05: Swiss scientists said they had discovered a form of star spinning at a record speed of 600 revolutions a second, feeding off a nearby companion star to maintain its energy. Astronomers from the University of Geneva said only five of that type of ravenous star had been discovered before, and none had such a spinning speed. "Part of a couple, this strange star absorbs its companion, a normal star, which gives it the energy necessary to spin so fast."
. . The pulsar was discovered by a university team using the European Space Agency's satellite Integral, launched in 2002, which is designed to observe gamma ray bursts.
Feb 1, 05: Recent research postulates that magnetars come from the death of very massive stars, which may mean that the dozen or so magnetars so far seen may be all our galaxy holds. The first one was discovered in 1998. Magnetars are an adolescent stage of neutron stars, but only 10% of neutron stars will go through the magnetar stage –-ruling out some theories that all pulsars spend some time as magnetars. There could be many more "dead" magnetars in the galaxy.
. . The original star, out of which the magnetar formed, had a mass 30 to 40 times that of the Sun. It lived only 5-6 million years before it exploded --about 3,000 years ago. Such a hefty beginning would help explain the difference between magnetars and their close cousins, pulsars. Pulsars are stellar corpses that serve as the radio lighthouses of the galaxy. Spinning around several times a second, they flash the galaxy with a beam of radio waves. Magnetars are similar, but they flash X-rays, and at a slower rate –-about once every 10 seconds. They also occasionally let out a burst of gamma rays.
. . There are about 1,500 known pulsars, but less than a dozen firmly identified magnetars. What makes magnetars special is their magnetic field, which is thousands of times stronger than that of normal pulsars and billions of times stronger than that of any magnet on Earth.
. . A rotating magnet gives off energy, and the greater the magnetic field, the faster the energy loss. Magnetars exhibit rapid deceleration, which implies a huge magnetic field. Gaensler has estimated that after 10,000 years, a magnetar will slow down enough to turn off its X-ray flash.
. . Magnetars are thought to originate from the supernova of very massive stars. An enormous void –-more than 70 light-years across-– that showed up in their radio data. A stellar wind from the progenitor star of the magnetar must have cleared out the gas. This wind would have been five times faster than Sol’s wind of charged particles --the source of space weather and the Northern Lights-- and a million times denser. The implied energy is 25 million times that of our solar wind.
. . "Astronomers used to think that really massive stars formed black holes when they died", said Simon Johnston from the Australia Telescope National Facility. "But in the past few years, we've realized that some of these stars could form pulsars, because they go on a rapid weight-loss program before they explode as supernovae."
. . Gaensler said that, at the very end of its life, the star likely lost 90% of its mass, which would make it skinny enough to become a neutron star, as opposed to a black hole.
Jan 31, 05: Shining brightly in the constellation Leo is a fast-spinning star that shoots through the cosmos like an extra-wide bullet, perplexing astronomers as it moves through space in the same direction as its polar axis. Regulus' axis is tilted about 86 degrees.
. . The brightest star in Leo, it spins much faster than Sol. Regulus is shaped by its high-speed rotation: 700,000 miles (1.1 million kilometers) an hour spin at its equator. With such a high rate of rotation --Sol, for comparison, has an equatorial spin of about 7,242 km an hour-- Regulus bulges out at the center to a diameter about 4.2 times that of Earth's home star. If Regulus spun just 10% faster it would rip itself apart, but that's not likely.
. . Although Regulus shines about 350 times brighter than Sol, it burns hotter at its poles (15,100 degrees Celsius) than at the equator (10,000 degrees Celsius), where the pull of gravity is diminished by the star's distorted shape, which in turn lowers the temperature. The poles shine five times brighter than the equator.
Jan 20, 05: Cosmic rays come from everywhere. Nobody has ever firmly tied a thing in the sky an ultra high-energy cosmic ray. (A separate recent study identified a source of lower-energy cosmic rays here in our own galaxy.) In the new research, Farrar and her colleagues identified five cosmic rays over a 10-year period that all come from one small circle in the sky. Observations of that same circle of sky reveal a colossal merger of two clusters of galaxies, about 450 million light-years away.
Jan 12, 05: "Hyper-Luminous Infrared Galaxies". Strange objects in faraway space known to astronomers only as Giant Galactic Blobs have, upon close inspection, become a lot weirder. The blobs are huge clouds of glowing gas. They've been puzzling astronomers since their discovery five years ago. Turns out there are typically two or more galaxies inside a given blob. The crowded region of space is a hotbed of galaxy formation. Understanding the blobs could help scientists understand how the universe evolved.
. . Three things might cause the blobs hydrogen to glow, Colbert said.
. . 1* Radiation from matter being superheated as it swirls into black holes at the galaxies' centers
. . 2* Superwinds of material from mass quantities of exploding stars
. . 3* Energy released by gas that cools as it falls into the center of a galaxy
In infrared, their inner galaxies turn out to be among the brightest in the universe, releasing 10 trillion times more energy than the Sun.
Jan 12, 05: Two teams of researchers, chiefly from Australia, Britain and the United States, have determined that galaxy formation occurrs at every 500 million light year interval, matching exactly the intervals between the Big Bang shock wave ripples observed when the cosmos was young.
. . "These ripples in the matter grew for a million years until the universe cooled enough to freeze them in place. We now see the corresponding cosmic ripples in the SDSS galaxy maps" -- Sloan Digital Sky Survey that has mapped 46,000 galaxies spread out over a distance of four billion light years. The two international teams have mapped some 260,000 galaxies.
Jan 11, 05: Astronomers are highly confident that they've taken the first photograph of a planet outside our solar system. The setup is about 225 light-years away. A new image from the Hubble Space Telescope confirms with a high degree of confidence a picture made previously by astronomers at the European Southern Observatory. It does not orbit a normal star --it's a brown dwarf-- and it is much more massive than the largest planets in the Solar system. The planet candidate is about 1.5 times the diameter of Jupiter and about five times as massive. It orbits the brown dwarf star at about 30% farther than Pluto is from our Sun. The brown dwarf does not have enough mass to trigger thermonuclear fusion and shine like a normal star, but it is also outside the realm of planethood, being some 25 times more massive than Jupiter and glowing with infrared light.
. . They are gravitationally bound, as originally suspected. They expect to be 99.9% sure in April when more Hubble observations are made as the planet presumably moves a bit farther along in its orbit.
. . Becklin, who was not involved in the imaging, said there is evidence for planets orbiting planets and planets floating alone in space with no star. If the latest image is proved to be what it seems, that would suggest "planets are around a lot of things", he said.
Jan 11, 05: A new study reveals that the center of our Milky Way Galaxy is loaded with black holes, as astronomers have expected in recent years. The galactic center is dominated by one supermassive black hole. It packs a mass equal to about 3 million Suns. Around it, scientists have expected to find a high concentration of stellar black holes, the sort that result from the collapse of massive stars. Each can be a few to many times the mass of the Sun.
. . Observations have hinted at the existence of many stellar black holes near the galactic center. But nosing around there is hard, because the region is shrouded in dust. Visible light doesn't escape the region. X-rays conveniently pierce interstellar dust.
. . They found strong evidence for seven black holes (they could be neutron stars, which are also very dense). Importantly, four of the objects were concentrated in the inner 3 light-years of space around the supermassive black hole.
. . "The observed high concentration of these sources implies that a huge number of black holes and neutron stars have gathered in the center of the galaxy." Extrapolating to the whole sky, the finding suggest a swarm of 10,000 black holes and neutron stars orbit near the galaxy's middle.
. . Mark Morris, co-researcher on the new project, predicted the concentration back in 1993. Dense objects like black holes interact gravitationally with less dense stars. The lighter stars tend to get jettisoned outward, Morris figured, while the black holes slow down on their orbital trek around the galactic center, and they sink inward.
Jan 10, 05: Black holes may actually drag the fabric of space and time around them as they spin, creating waves for cosmic material to surf on, astronomers said. This is new evidence that some black holes spin, even as they pull in everything around them, including light. One characteristic that astronomers watch at the mouth of black holes is the flickering of X-ray light. It would make sense that the flickers would come very fast, since black holes spin so rapidly. It was more puzzling when the flickering X-rays came more slowly, at as little as one 100th the speed of the fast flickers, Miller told reporters at a meeting of the American Astronomical Society.
. . Miller and his colleagues theorize that in one black hole system they studied, the slower flickering could be the frequency of a space-time warp. In that case, the flickers --known as quasi-periodic oscillations-- could be caused by the fabric of space itself churning around the black hole in a wave. "Gas whipping around the black hole has no choice but to ride that wave."
. . By looking at iron atoms, which are good markers for what is occurring around a black hole, the scientists figured that these three sun-sized blobs made one complete trip around the black hole in a day, at speeds up to 30,000 k per second. Since these blobs were about as far from the black hole as Jupiter is from the sun, this was remarkable.
. . The whole system that includes the black hole is relatively tiny, about the size of the solar system.
Jan 10, 05: A trio of supergiants --red, cool, bright stars at the end of their lives-- may be the biggest stars ever identified, astronomers reported. All three have diameters of more than 1.5 billion km, or 1,500 times the sun's girth. The big three dwarf even Betelgeuse. They would completely engulf Earth and their outer layers would extend to a point between the orbits of Jupiter and Saturn. All the stars in the study were single stars, not binaries.
. . Determining their size was more a matter of computer modeling than telescope observing. In the case of stellar temperatures, cool is a relative term. These stars are around 5,600 degrees Fahrenheit. The sun is nearly 10,000 degrees F and the hottest known stars are more than 90,000 degrees F.
. . Knowing the temperature was important, because a fundamental law of stellar physics holds that a star's brightness is proportional to its temperature and size. By knowing two of these numbers, scientists could find out the third with precision. The trio were about 10% warmer than researchers had expected.
. . Will this ever happen to our sun? In a word, no. Sol simply lacks the mass to become a red supergiant.
Jan 10, 05: Few objects in the sky have more magnetic personalities than planetary nebulas. The Hubble Space Telescope and others have produced stunning images of the zoo of bizarre shapes and intense colors these objects display. A new study seems to confirm one crucial aspect of what's behind the mysterious shapes, that they are sculpted in large part by the magnetic field of the dying star that spawns them.
Here's what's known about how they work:
. . A wind of charged particles continues to flow from the aged star, and the wind runs into the previously ejected layers, creating shock waves. Radiation from the star ionizes atoms in these outward-racing crash sites. Electrons recombine with the ions and emit light.
. . But how does the process form such bizarre shapes? Only 20% of planetary nebulas are spherical, with stuff heading out more or less evenly in all directions. Many of the rest take on various versions of the classic hourglass shape. Astronomers call them bipolar. One of the most well known is the Dumbbell Nebula, whose name aptly describes its form. Others are elliptical.
. . Theorists have assumed that lingering magnetic fields, remains of the days when the central star was normal, shape the outflow. Computer models show this to be the best explanation.
. . New observations appear to clinch the magnetism case, more or less.
. . And what about those 20% of planetary nebulas that are spherical? "A very good question", Jordan says. "Our unproved hypothesis is that the larger the magnetic field is the larger the deviation from spherical symmetry."
The more the universe expands, the more dark energy there is to make it expand even faster, ultimately leading to a runaway cosmos.
. . Dark energy makes up a full 73% of everything in the universe. Dark matter makes up 23%. The matter we are familiar with --the stuff of planets, stars, and gas clouds-- makes up only about 4% of the universe.
. . The stars will exhaust their nuclear fuel, galaxies will cease to illuminate the heavens, and the universe will be littered with dead dwarf stars, decrepit neutron stars, and black holes. The most advanced civilizations will be reduced to huddling around the last flickering embers of energy --the faint Hawking radiation emitted by black holes.
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