Distant Quasar Extends ‘Edge’ of the Universe

Astronomers have found what they believe to be the most distant object ever seen, a quasar so far away that it challenges current theories that the universe has an “edge.”

The quasar, which is a starlike object that radiates immense quantities of energy, is more than 12.4 billion light years away, about 10 million light years farther than the farthest object found previously. A light year is the distance light travels in a year, about 6 trillion miles.

Quasars have long fascinated scientists because they are believed to be the oldest and most distant objects in the observable universe. They are seen in giant telescopes as they were billions of years ago because it has taken that long for their light to reach Earth.

The discovery also indicates that there are far more quasars than previously thought, but scientists just have not been looking for them in the right way, according to one of the astronomers who made the discovery, Wallace L. W. Sargent of Caltech.

Sargent, Cyril Hazard of the University of Pittsburgh, Alexei Filippenko of UC Berkeley, Richard McMahon of University of Cambridge, England, and Charles C. Steidel, also of Caltech, report their findings in today’s issue of Nature, the British scientific journal.

A number of astronomers have worked hard in recent years to find more distant quasars, but they have been unsuccessful, thus lending support to theories that the universe has a sharp edge. The edge, astronomers have suggested, is made up of quasars.

By using a new technique, Sargent and his colleagues discovered the new quasar 10 million light years farther out, indicating that if there is an edge, it is a ragged edge, and it is not where astronomers had thought it was.

Furthermore, astronomers have thought that all quasars originated at the same time, in the earliest stages of the universe. If that is true, quasars that are more distant from the Earth should be dimmer simply because they are farther away.

But the new quasar, known only by a number, Q1208+1011, is about as bright as many of those discovered earlier, even though it is much farther away. That indicates the quasars did not all turn on at the same time, and some are simply younger than others.

Since they were first discovered in the 1960s, astronomers have found about 3,500 quasars, and that number was not expected to grow significantly.

But the latest discovery “indicates the number of quasars is really bigger than people thought before,” Sargent said.

Although they are intensely bright in terms of the energy released, quasars are so far away that they appear extremely dim, even in large telescopes. The one announced today is about 50,000 times too faint to be detected with the naked eye.

In recent years, astronomers have searched for more distant quasars by concentrating on faint, narrow areas of the sky. The idea was that more distant quasars would be so dim that they could only be found through a painfully tedious process of carefully searching dim, narrowly focused areas.

The Sargent team used two telescopes on two continents--the wide-field United Kingdom Schmidt telescope in Australia and Caltech’s 200-inch Hale Telescope at Palomar Observatory in Southern California--to make their discovery.

The team used the wide-field telescope to find suspected quasars and the more powerful Palomar scope to confirm it. The wide-field telescope was adapted with a prism that breaks down the light from a celestial object into its component colors, providing a spectral “signature” of the object. Astronomers can tell by the signature whether they are looking at such things as a galaxy, a star or a quasar.

By scanning a wider area of the sky, the Australian telescope identified a number of targets that bore the signature of quasars. The team then turned the Palomar giant toward the suspects, one by one, and discovered the new quasar.

“The method we’ve used to find this object could be extended” to quasars that are even much farther away, Sargent said. “We are continuing our search.”