Printer Friendly

Hidden black holes.

Astronomers have new evidence that a majority of the biggest black holes in the universe lie hidden behind thick veils of dust.

Monster black holes, which reside at the centers of galaxies, betray their presence when their immense gravity induces surrounding matter to generate a brilliant beacon of light known as a quasar. Models of the quasar light suggest that these beacons make a large contribution to the overall X-ray glow of the sky. However, the number of individual quasars actually observed in X-ray and visible-light studies falls far short of the expected population.

Researchers have proposed that the shortfall comes about because many quasars are shrouded by their own dusty rings or because they reside in dust-drenched galaxies that keep the beacons' visible light and even their X rays hidden from astronomers.

Infrared light, however, can make it through even a thick layer of dust. Using a sensitive infrared observatory, the Spitzer Space Telescope, researchers have uncovered 21 previously unknown quasars in a small patch of sky. By extrapolating that number to the entire sky, Alejo Martinez-Sansigre of the University of Oxford in England and his collaborators came up with the predicted number of quasars in the cosmos.

Black holes that accumulate huge masses do so at the cores of dusty, starforming galaxies, the Oxford team asserts in the Aug. 4 Nature. Another team, led by Jennifer Donley of the University of Arizona in Tucson, describes similar Spitzer findings in an upcoming Astrophysical Journal.
COPYRIGHT 2005 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Science News
Article Type:Brief Article
Geographic Code:1USA
Date:Sep 3, 2005
Words:245
Previous Article:Rice, revealed.
Next Article:Placebo reins in pain in brain.
Topics:


Related Articles
Huge black hole may lurk in nearby galaxy.
Hubble captures a violent universe.
Galactic black hole: X marks the spot?
Orbiting Hubble eyes active galaxy's disk.
News Flash: Astronomers Demystify Gamma-Ray Bursts.
Massive black holes let there be light.
Are midsize black holes the missing link? (Hole in the Middle).
Sounding out a new role for black holes.
A black hole's dusty environs show themselves.
Crash: ripples of space-time debut in black hole simulations.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters