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Astronomers detect distant quasar near outer limits of our universe
13 Apr 2000

By Robert Sanders, Media Relations

BERKELEY -- Astronomers taking advantage of the unparalleled light-collecting power of the Keck Telescope in Hawaii have found the most distant object in the universe, a quasar that must have been among the first objects ever to form, according to an astronomer at the University of California, Berkeley.

Quasars are thought to be the early stages of galaxy formation, seen today as bright but distant star-like objects. They are thought to be fueled by a central black hole in a feeding frenzy, gobbling up stars and emitting copious amounts of energy.

This particular quasar, named SDSS 1044-0125, was identified as a possibly distant quasar from data taken by the Sloan Digital Sky Survey (SDSS) in March of this year, said survey spokesperson Michael S. Turner of the University of Chicago and the U. S. Department of Energy's Fermi National Accelerator Laboratory (Fermilab).

Last week a team of astronomers led by Marc Davis, the professor of astronomy at the University of California, Berkeley, obtained spectra of the object at the Keck II Telescope in Hawaii and confirmed that it is a distant quasar.

With a redshift of 5.8, the light we see was emitted about a billion years after the birth of the universe, when it was 6.8 times smaller than it is today, Davis said. A redshift of 5.8 means the wavelength of light was shifted by 580 percent.

"It's astounding," Davis said. "This is very close to the limit we should be able to see in the universe."

Davis's colleagues at the 10-meter Keck II telescope, which together with Keck I are the largest optical and infrared telescopes in the world, were Robert Becker of the UC Davis, Princeton graduate student Xiaohui Fan and Dr. Richard L. White of the Space Telescope Science Institute in Baltimore, Md.

Davis said that quasars at this distance should be extremely rare, and he is surprised that it was even detected. At about a million to 10 million times the mass of our Sun, it is amazingly bright.

"Our first question is, 'How does a thing like this get built and form a black hole at the center in such a short time?'" he said. "Based on our current understanding of how the universe evolved, bright quasars like this shouldn't exist at such a distance, or they should be very rare."

The quasar is so distant that the expansion of the universe shifted its light, originally emitted as ultraviolet, through the visible into the infrared part of the spectrum.

"Anything much farther away will be shifted so far into the infrared that it will be beyond the ability of our instruments to detect," he said.

Twice before, Sloan survey scientists have found quasars that have broken the distance record. To date, the survey has discovered thousands of quasars, including eight of the 10 most distant known quasars and two-thirds of the quasars with redshifts greater than 4.5.

According to Richard Kron of the University of Chicago and Fermilab, the SDSS quasar advantage comes from the size of the survey and its unique ability to look at objects across five precisely measured color bands. The survey digitizes images of 20,000 objects in every square degree of sky, and automated algorithms select quasar candidates based on this color information. Distant quasars take on the appearance of very red stars.

Scientists hope to use quasars to chart the birth and formation of galaxies, explore structure on the largest scales, and better understand black holes. Already, said Princeton's Fan, he and others have used the early Sloan sample to trace the time history of quasar populations. Consistent with earlier studies, the SDSS data show that the number of quasars rose dramatically from a billion years after the Big Bang to a peak around 2.5 billion years later, falling off sharply at lower redshift and, hence, later times.

The Sloan project will ultimately survey one quarter of the sky and 200 million objects. A million or so of these will be quasars, which numerous telescopes around the world will study further.

The Sloan Digital Sky Survey is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Max-Planck-Institute for Astronomy, Princeton University, the United States Naval Observatory, and the University of Washington. Funding for the project has been provided by the Alfred P. Sloan Foundation, the SDSS member institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, and Monbusho.

The W. M. Keck Observatory, perched on the summit of Hawaii's dormant Mauna Kea volcano, is operated by the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The telescopes, Keck I and II, were made possible through grants totaling more than $140 million from the W.M. Keck Foundation.



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