Sextans quasar is
most distant object yet
By Diane
Ainsworth, Public Affairs
Posted April 26, 2000
A quasar in the constellation Sextans, so luminous that it can be seen 12 billion light years from Earth, may be the oldest, most distant object yet observed by scientists.
A team of astronomers, led by Berkeley's Marc Davis, confirmed the discovery April 13, using data collected by the Keck II Observatory atop Mauna Kea, Hawaii. Appearing as a miniscule pinpoint of red light in spectra from the behemoth, 33-foot optical telescope, the object probably started emitting its energy when the universe was less than a billion years old.
"We were astounded to find this object," said Davis, who worked with colleagues from UC Davis, Princeton, the University of Chicago, Fermilab in Batavia, Ill., the Keck Observatory and the Hubble Space Telescope Science Institute, Baltimore, Md., on a spectral analysis of the object's light. "This breaks the record for the most distant object ever observed, and it's very close to the limit of our observing capabilities any place in the universe."
At 12 billion light years away, the quasar, dubbed SDSS 1044-0125, is one of the earliest structures to form when galaxies were young and the first light appeared in the universe. The universe is thought to be 13 billion years old, which places the quasar's birth at about a billion years after the Big Bang.
Quasars are powerhouses of the cosmos, extremely luminous bodies that were more common in the early universe. The objects, which are emissions of light from matter pouring into massive black holes at the center of a galaxy, are packed into a volume roughly equal to the solar system. One quasar can emit an astonishing amount of energy -- up to 10,000 times that of the whole Milky Way galaxy. Scientists believe that quasars gobble up fuel from these super-massive black holes, which eject enormous amounts of energy as they consume surrounding matter.
Observing these tiny pinpoints of light at such vast distances, even with the most powerful optical telescopes and orbiting satellites, is akin to looking into the headlights of an oncoming car in a snowstorm and trying to identify its manufacturer.
"The newly discovered object has a redshift of 5.8, the highest ever measured," Davis said. "In fact, it was too red to be seen by the human eye, even with the most sophisticated equipment." The first observations were made using data from the Sloan Digital Sky Survey, an ambitious effort by an international team of scientists to map half of the northern sky. Princeton graduate student Xiaohui Fan then obtained spectrum from the Keck telescope to confirm the discovery.
A quasar's "redshift" measures how fast the object is moving away from Earth as the universe expands, and is the best indicator of cosmic distances to date. The faster it moves away, the more its light shifts to the red part of the spectrum (toward longer wavelengths). At a redshift of 5.8, light traveling from SDSS 1044-0125 journeyed about 12 billion light years to reach earth. A light-year is the distance light travels in a year, about 6 trillion miles.
"At that distance," Davis said, "we're guessing the luminosity of this quasar is around 100 trillion times the luminosity of the sun, which is amazingly bright."
Scientists, in their efforts to explain the origins of quasars, theorize that most galaxies contain massive black holes capable of generating vast amounts of energy under special circumstances. The energy production rises dramatically when gas and stars start falling into the black holes at an increased rate. This massive inward spiraling usually occurs with galactic collisions or near misses. Quasars were thus more prevalent in the epoch of high galaxy density, when the universe was much younger and more crowded than it is today.
The first challenge for astronomers is to understand how an object like this is formed in such a short amount of time.
"Based on our current understanding of how the universe evolved and how much it has expanded, bright quasars like this shouldn't exist at such a distance, or they should be very rare," Davis said. "This discovery is likely to help us better understand how matter was distributed at earlier stages of cosmic history."
April 26 - May 3,
2000 (Volume 28, Number 30)
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