SEATTLE - The most distant quasar known ceded its title today as yet another of these compact, bright galaxies -- even farther away, nearly at the edge of the observable universe -- was captured by astronomers.
Images from the Sloan Digital Sky Survey have yielded several distance records in recent years. The newest record-setting quasar is seen as it was when the universe was only about 800 million years old, or roughly 13 billion years ago. This means its light took 13 billion years to reach us.
Quasars are compact but bright. They are essentially galaxies powered by supermassive black holes that scientists think are activity swallowing large amounts of matter, the equivalent of 10 to 20 stars every year. Because most are so far away, however, astronomers know little about them, except that they seem prevalent in the early universe.
.The finding was announced here today at a meeting of the American Astronomical Society by study leader Xiaohui Fan of the University of Arizona.
In astronomers' parlance, the quasar is at a redshift of 6.4. Redshift works this way: When an object is moving away from Earth, its light waves are stretched and become redder. Because the universe is expanding, the farthest objects are moving away the fastest, relative to Earth.
Astronomers examine how red the light is to help determine distance.
The previous record-holder, announced in 2001, was at redshift 6.28. Also today, the same astronomers said they'd uncovered a quasar at redshift 6.2 and another at 6.1. All together, Sloan is now responsible for the seven most distant quasars.
"The Sloan Survey has generated a sample of quasars which stretches through all of cosmic time, from 800 million years after the Big Bang to the present," said James Gunn, a Princeton researcher who is project scientist for the survey. "These data will be invaluable for the next major effort of the Sloan Survey quasar team, namely to characterize the evolution of quasars from their formation to the present.
In a separate study, normal galaxies were discovered at great distances, too, mingling with the quasars and helping astronomers better grasp the early universe. Meanwhile, in a third study, a nearby quasar has been examined in unprecedented detail by the Hubble Space Telescope.
The recently installed Advanced Camera for Surveys aboard Hubble was directed to peer into the heart of a relatively nearby quasar called 3C 273. The camera has a device the blocks light from the central, brightest portion of a quasar, allowing it to see detail in the rest of the object.
Johns Hopkins University's Andre Martel and colleagues were surprised to find more complexity than expected in 3C 273. The images reveal a spiral plume wound around the quasar, along with a red dust lane, a blue arc, all features that has not been seen before.
Meanwhile, back near the edge of the universe, several normal galaxies were found by Hubble in a study led by Hao Jing Jan, a Ph.D. student at Arizona State University. Jan and his adviser, Rogier Windhorst, discovered about two dozen galaxies around a redshift of 6. These galaxies are not as active as quasars, and appear to be smaller, lighter versions of normal galaxies like our own Milky Way.
The combined discoveries suggest that galaxies and quasars co-existed in the first years of the universe, said Meg Urry, a Yale University researcher who was not involved in either study.
Quasars are probably a phase of galaxy formation, Urry said, and the distant galaxies seen by Hubble have probably already had a quasar phase.
All this bears on how and the very first galaxies were formed, those presumed to exist even farther away than the current record-holders. It is not known how small the first galaxies were, or exactly when the first black holes developed inside them, which formed first, or when.
Astronomers do have good evidence the universe was
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