| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
03 Aug 2005 01:00:40 PM |
| Object: |
NASA's Spitzer Finds Hidden, Hungry Black Holes |
Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Dolores Beasley (202) 358-1753
NASA Headquarters, Washington
News Release: 2005-128 August 3, 2005
NASA's Spitzer Finds Hidden, Hungry Black Holes
Most of the biggest black holes in the universe have been eating cosmic
meals behind closed doors -- until now.
With its sharp infrared eyes, NASA's Spitzer Space Telescope peered
through walls of galactic dust to uncover what may be the long-sought
missing population of hungry black holes known as quasars.
"From past studies using X-rays, we expected there were a lot of hidden
quasars, but we couldn't find them," said Alejo Martínez-Sansigre of
the University of Oxford, England. He is lead author of a paper about
the research in this week's Nature. "We had to wait for Spitzer to find
an entire population of these dust-obscured objects."
Quasars are super-massive black holes that are circled by a giant ring
of gas and dust. They live at the heart of distant galaxies and can
consume up to the equivalent mass of one thousand stars in a single
year. As their black holes suck in material from their dusty rings, the
material lights up brilliantly, making quasars the brightest objects in
the universe. This bright light comes in many forms, including X-rays,
visible and infrared light.
Astronomers have puzzled for years over the question of how many of
these cosmic behemoths are out there. One standard method for
estimating the number is to measure the cosmic X-ray background.
Quasars outshine everything else in the universe in X-rays. By counting
the background buzz of X-rays, it is possible to predict the
approximate total number of quasars.
But this estimate has not matched previous X-ray and visible-light
observations of actual quasars, which number far fewer than expected.
Astronomers thought this might be because most quasars are blocked from
our view by gas and dust. They proposed that some quasars are
positioned in such a way that their dusty rings hide their light, while
others are buried in dust-drenched galaxies.
Spitzer appears to have found both types of missing quasars by looking
in infrared light. Unlike X-rays and visible light, infrared light can
travel through gas and dust.
Researchers found 21 examples of these quasars in a small patch of sky.
All the objects were confirmed as quasars by the National Radio
Astronomy Observatory's Very Large Array radio telescope in New Mexico
and by the Particle Physics and Astronomy Research Council's William
Herschel Telescope in Spain.
"If you extrapolate our 21 quasars out to the rest of the sky, you get
a whole lot of quasars," said Dr. Mark Lacy of the Spitzer Science
Center, California Institute of Technology, Pasadena, Calif., a
co-author of the Nature paper. "This means that, as suspected, most
super-massive black hole growth is hidden by dust."
The discovery will allow astronomers to put together a more complete
picture of how and where quasars form in our universe. Of the 21
quasars uncovered by Spitzer, 10 are believed to be inside fairly
mature, giant, elliptical galaxies. The rest are thought to be encased
in thick, dusty galaxies that are still forming stars.
A team of researchers based at the University of Arizona, Tucson, found
similar quasars using Spitzer. Their research is described at
http://uanews.org/science .
Other authors of the Nature paper include Drs. Steve Rawlings and Matt
Jarvis, University of Oxford; Drs. Dario Fadda and Francine Marleau,
Spitzer Science Center; Dr. Chris Simpson, University of Durham,
England; and Dr. Chris Willott, National Research Council Canada,
Victoria.
The Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech,
manages the Spitzer Space Telescope mission for NASA's Science Mission
Directorate, Washington. Science operations are conducted at the
Spitzer Science Center at Caltech. Spitzer's multiband imaging
photometer, which observed the quasars, was built by Ball Aerospace
Corporation, Boulder, Colo.; the University of Arizona; and Boeing
North America, Canoga Park, Calif. Spitzer's infrared array camera,
which also observed the quasars, was built by NASA Goddard Space Flight
Center, Greenbelt, Md.
A Spitzer false-colored picture of one of the newfound quasars is
available at http://www.spitzer.caltech.edu/Media/index.shtml .
For information about NASA and agency programs visit
http://www.nasa.gov/home/ .
-end-
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