The Cosmic Mirrorof News events across the Universe |
Compiled and written by Daniel Fischer, Skyweek - older "Mirrors" in the Archive - and find out what the future might bring! The latest issue! |
Current mission news: MGS (science!) + Cassini + Galileo + Prospector |
Eta Carinae's surge in brightness stuns astronomersRarely ever have astronomers had to confess their puzzlement at an astronomical more than about the recently discovered rapid brightening of the southern star Eta Carinae (see small items of Update #127): This star is just not supposed to do that! At a dramatic news conference at the meeting the astronomers involved in the discovery freely admitted their bewilderment. From late 1997 til early 1999 the star has doubled its brightness, to a visual magnitude of 5.2 - and nobody noticed it until spectra from Hubble's STIS instrument from different years were analyzed quantitatively this spring.That alone - a Hubble discovery that everyone (South of 20 deg.N) can see naked-eye - is remarkable enough. But what makes the Eta Car event really special is that it cannot be, astrophysically speaking. Even before the brightening the star was shining close to the so-called Eddington limit (at which the radiation pressure would tear it apart). The STIS spectra are literally overwhelming in their complex detail, some involving atomic physics never seen in space, but they don't give a clue to what has caused the sudden brightening of the star. And no one dares to predict what its brightness will do next - are we in for another big eruption like in 1837-60? (News conference and posters at the Meeting on June 2nd) |
U of MN, GSFC Press Releases and the original IAUC alert. News coverage from ABC and MSNBC. Also: Eta Car - an introduction. Unrelated Eta pages from Damineli, Morse and Bish. |
New doubts about the Hubble constantNew controversy has erupted (kind of) at the 194th Meeting of the American Astronomical Society: Could it be that all studies of the Hubble constant, that seemed to converge nicely near a value of 70 (see last Update), are off by 15% - because we've got the distance of the Large Magellanic Cloud wrong? The famous 'cosmological distance ladder' is based to a large degree on the distance of the LMC, usually set at 50 kpc (or a distance modulus of 18.5). In that galaxy, numerous Cepheid variables are found - and used to calibrate their period/luminosity relation that is then used to get distances to other galaxies where Cepheids are detected. If the 'short' distance to the LMC (modulus 18.2) should turn out to be correct, as new research with the Very Long Baseline Array suggests, than the Hubble constant would jump up by 15%!At the same time that the Hubble Key Project team explained in a lengthy technical session how it had arrived at a final value for the Hubble Constant of 71 +/- 3 (random error) +/- 7 (systematic error), a dynamic young radio astronomer presented his distance determination for a remote galaxy at a news conference - with a method that does not use the LMC-based Cepheids. It does not employ Cepheids at all! J. Herrnstein used the proper motion of highly concentrated maser sources in the central disk of NGC 4258 - and Kepler's laws, of course - to obtain a purely geometrical distance estimate of 7.2 +/- 0.3 Mpc for the galaxy. And the classical Cepheid method had yielded 8.2 to 8.9 Mpc! If this surprising result holds and points to a deeper problem, the LMC is the likely culprit, and a general revision of all distance scales based on its distance (and the Cepheids) could be an unavoidable consequence. The Ho Key Project agrees here: The uncertainty of the LMC distance is their major unresolved problem, but one case like NGC 4258 won't convince them. Unfortunately its masers and their geometry are rather unique, so further Cepeheid-free distance determinations to other galaxies won't be forthcoming. But if a downward revision of the LMC distance should become necessary indeed, the Hubble constant would jump to around 82, as all the 4 methods employed by the Key Project are ultimately linked to it... (Talks by the Key Project team and news conference by VLBA scientists at the Meeting on June 1st and talk by Herrnstein on June 2nd) |
NRAO Press Release on the Herrnstein work. Abstract of the Herrnstein paper Hail to the VLBA! The Ho session News coverage about the new Hubble constant debate from Florida Today, MSNBC and the ABQ Journal. |
Two isolated really cool Brown Dwarfshave been discovered by two different teams in the first two percent of data from the Sloan Digital Sky Survey: They appear as extremely faint and extremely red points of light, best visible in the near-infrared 'z' band images. First taken as candidates for quasars with very high redshifts, the objects soon stood out with their most unusual spectra, unlike any star. The spectra are dominated by emission features from water vapor and methane, proof that the objects are very cool (about 900 Kelvin). Only one Brown Dwarf in orbit around and ordinary star (Gliese 229B) and our planet Jupiter have comparable spectra. (News conference at the Meeting on May 31st)
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Press Release on the Methane dwarfs. SDSS homepage ABQ Journal Story. |
| Four more Methane Brown Dwarfs have been announced shortly thereafter, bringing the known total to 7: They were found by another major sky survey, the "2MASS". After sorting through millions of celestial objects, the 'failed stars had been located in images taken by a pair of 1.3-meter telescopes in Arizona and Chile. They were then checked with the Keck Telescope atop Mauna Kea, to look for the presence of methane, the telltale chemical fingerprint of the coolest brown dwarfs. Among other 2MASS findings are many more "L stars", also very cool (but real) stars that belong to a new spectral class defined just one year ago (see Update # 83). Those mini-stars are at least as frequent as 'normal' ones. |
JPL Press Release and more details. Papers on 2MASS' Brown Dwarfs and L dwarfs. More 2MASS pictures and tons of data... |
Solar Maximum: Predictions agree on early 2000There is a virtually universal consensus now that the next solar maximum will occur in early 200 - with an intensity comparable to the two preceding maxima, i.e. with a smoothed sunspot number reaching 160. More than two dozen methods for predicting the solar activity had already agreed on that some years ago, and now a novel approach by Dick Altrock matches the predictions, too. Last year he had surprised many with predicted maximum already in 1999 (see Update # 98), but now he has changed that to March 2000 +/- one month. The reason: The speed with which the coronal features he uses "rush to the poles" was not established well enough. But now the 'pole rush' of the forerunners of (current) cycle # 23 can be tracked precisely, and the prediction of the time of maximum activity (15 months before the features reach the pole) has been updated. The first forerunners of cycle # 24 have also been spotted in the coronal data - the solar cycles do overlap a great deal, no doubt about that! (News conference at the Meeting on May 31st) |
SunspotCycle.com. A paper by Altrock on his method and a press release about it. Today's Space Weather. News coverage of possible consequences from ABC, ABQ Journal, CNN and Astronomy. |
The end is near for Mir ...The Russian Space Agency has failed to find a buyer for the aging space station, it now seems clear: The current crew will abandon it in August, the station will fly on for a few more months - and then reenter the atmosphere in February or March of 2000. To make sure that this takes place in a controlled manner, a new (or refurbished) computer should be installed, allowing full remote control - but questions have been raised whether that will work and whether Russia can afford it. |
ABC, BBC, CNN stories on the end of Mir. |
| Meanwhile the 2nd ISS visit by shuttle astronauts took place without problems. Afterwards the STARSHINE satellite was deployed on June 5th, and on June 6th Discovery performed a rare night landing at KSC. The launch preparations for the Chandra X-ray Observatory have resumed in the meantime, with a target launch date for Columbia of July 20th at the earliest. |
ISS mission: Some ESC pictures and coverage from CNN, BBC, ABC, SpaceViews. STARSHINE: Homepage, information and observers' page! Chandra: status on June 8th. |
Prospector's July lunar crash confirmedLunar Prospector's mission will come to an end in late July when the spacecraft is deliberately crashed into a lunar crater in an effort to observe water ice, NASA has confirmed June 2nd: Univ. of Texas, ARC and NASA news releases; news coverage from BBC, MSNBC and SpaceViews.Meanwhile a detailled analysis of ice deposits on the lunar poles has been performed using radar. The results have now been published: Cornell, NASA Press Releases, ABC, BBC stories, ice on the Moon in general. The Moon has a sodium tail that is caused by micrometeorite hits - and was particularly bright after last year's Leonid shower: BU Press Release, BBC, CNN stories. India wants a lunar mission, too - but not before 2008. Scientists there are convinced that the PSLV rocket could shoot a 250 kg space probe onto a fly-by trajectory or bring a 130 kg satellite into orbit. The science would resemble Lunar Prospector's. (Space News May 31, 1999) A power surge killed WIREAn unexpected power surge from a $2000 electronic circuit made the telescope cover pop off prematurely shortly after the launch of the small infrared satellite, dooming the mission: The phenomenon - that led to the explosion of the cover's pyrotechnic bolts - had not been detected in ground tests. ABC Story. |
(lots more to come in future Updates) Striking detail in the Trifid Nebulahas been revealed by the HST: There are lots of similiarities with the famous picture of the Eagle Nebula - and there is even a bright jet coming out of one of the (invisible) young stars. AZ State Univ. Press Release with all images!Adaptive Optics deliver super-sharp views of the Sunwith resolution approaching 1/10 of an arcsecond: A new system has been installed at the big solar telescope at Sac Peak. Here is the Homepage.All volumes of the ApJ are scanned!Never more need lazy astronomers go to the library: Each and every page of the Astrophysical Journal has now been digitized and is freely available at the Astrophysics Data System.
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Compiled and written by Daniel Fischer