Astro News Briefs: April 8–14

Editor's Note: This week astronomers from around the world have gathered at Bristol University in Bristol, England, for the annual United Kingdom National Astronomy Meeting. The following Astro Briefs highlight news items reported at the conference.

All Black Holes Sing the Same Song

April 9, 2002 | Using the Rossi X-ray Timing Explorer (RXTE) satellite, University of Southampton astronomers Phil Uttley and Ian McHardy observed varying X-ray emissions from gas falling into both the supermassive black holes in the centers of galaxies and the million-times-smaller black holes that result from collapsed stars. The astronomers find that the two very different sizes of holes show nearly identical patterns of X-ray variations. The only difference is the variations' speed — from fast in the case of low-mass holes to slow for the large ones. The speed seems to scale precisely with the holes' masses and sizes. This is an encouraging sign that by studying events that happen in stellar-mass black holes on time scales from milliseconds to years, astronomers can learn about events that happen in quasars on much longer time scales of up to millions of years, as described in the May Sky & Telescope, page 32.

Details are in a press release at
http://www.star.bris.ac.uk/nam/press/release3.html.


Massive Elliptical Galaxies Matured Early

April 10, 2002 | Using the Hubble Space Telescope, a team of astronomers from the University of Edinburgh and Oxford University have examined several quasars seen when the universe was about 1/3 its present age (redshift 2 to 3). During a five-year study, a team led by Marek Kukula (Edinburgh University) confirmed that, as others have found, quasars seen late in the universe's history tend to reside in massive, giant elliptical galaxies. However, it had not been clear that young quasars at a redshift of 3 would also occur in such environs. The finding that they do indicates that elliptical galaxies evolved to maturity much faster than previously expected and were bright and full of newly formed stars at very early epochs.

More information is in a press release at
http://www.ras.org.uk/press/pn02-10.htm.


Stellar Gas Jets Light Up Clouds

April 10, 2002 | Astronomers have long observed narrow gas streams coming from newborn stars. When such a stream hits an interstellar cloud, the shock of impact lights up the target. Scientists call these bright shock fronts Herbig-Haro (HH) objects. Recently Serena Viti (University College London) and colleagues observed HH objects at radio wavelengths to determine their chemical makeup.


Extra-Luminous Galaxies Contain Extra Dark Matter

April 10, 2002 | Computer simulations by Ofer Lahav (Cambridge University) and colleagues predict that the more luminous a galaxy is, the more dark matter it ought to contain. Because of this additional mass, the brightest galaxies should be more condensed and should cluster together more than "average" galaxies. Comparing their simulations to the 220,000 galaxies observed so far by the massive Two-Degree Field Galaxy Redshift Survey (2dF), the astronomers find that brighter galaxies do tend to cluster together much more than dimmer objects.

Details are in a press release at
http://www.ras.org.uk/press/pn02-20.htm
Images of the computer simulations can be found at
http://star-www.dur.ac.uk/cosmology/theory/ICC/Press/March2002/


Neutrino Weigh-in

April 10, 2002 | Astronomers analyzing galaxy clumping in the 2dF survey have also concluded that the universe's dark matter can consist of no more than 1/5 neutrinos. This means the miniscule elementary particles can weigh no more than one billionth of a hydrogen atom (no more than 1 electron volt). Yet recent experiments have proven that they do have some mass. The team, led by Ofer Lahav (Cambridge University), compared the distribution of galaxies in the 2dF with computer models of the cosmos featuring various masses for the neutrinos that should be left over from the Big Bang.

More information is in a press release at
http://www.ras.org.uk/press/pn02-13.htm.


A Possible Home for an Extrasolar Earth

April 10, 2002 | Although astronomers have found about 80 extrasolar planets, none is anything like Earth. All are gas giants as massive as Saturn, Jupiter, or more, and many are in strongly elliptical orbits. However, one exoplanet system, 47 Ursae Majoris, does bear a resemblance to our solar system. Its two known planets circle closer to the star than Jupiter does to the Sun, but their comparative orbit sizes and mass ratios are reminiscent of Jupiter and Saturn (the planets have 2.5 and 0.76 Jupiter masses, respectively). Astronomers assumed that such massive objects would disrupt the orbit of any small, Earthlike planet in the star's habitable zone, the area where the temperature is right for liquid water. Not so, say Barrie Jones and Nick Sleep (The Open University, England). They found several stable orbits possible in the habitable zone. This makes 47 UMa an enticing target for future searches for Earth-sized exoplanets.

More on the astronomer's work is in a press release at
http://www.ras.org.uk/press/pn02-13.htm.


Astronomers Uncover Stellar Graves

April 11, 2002 | Astronomers conducting a survey of the night sky in hydrogen-alpha light using the Anglo-Australian Observatory's UK Schmidt Telescope have uncovered a wealth of planetary nebulae in the southern part of the Milky Way. After scanning about 70 percent of the galactic plane, Quentin Parker (Royal Observatory Edinburgh) and Steven Philipps (University of Bristol) uncovered nearly 1,000 new planetaries and a slew of other objects including 8 new Wolf-Rayet stars. The survey has doubled the known population of planetary nebulae and help future astronomers better understand the transition phase from planetary nebula to white dwarf during a stars death throes.

More information can be found at
http://www.ras.org.uk/press/pn02-22.htm