After just five days of observations at their New Mexico observatory last summer, astronomers discovered what they say are the two most distant quasars ever observed, plus another now ranked No. 4.
A member of the international Sloan Digital Sky Survey team, which includes the Johns Hopkins University, where news of the discovery was released yesterday, said the new quasars were ** detected at perhaps 15 billion light-years from Earth -- so distant that the light must have left the quasars when the universe was just 5 percent of its present age.
"I just sort of jumped out of my chair" on hearing the news, said Alex Szalay, a professor of physics and astronomy at Hopkins. To make such discoveries while debugging its new equipment "shows that the Sloan project is going to fundamentally change astronomy."
"What is also very exciting," he said, "is that we knew these quasars existed close to that [distance]. But among the 100 million objects we are going to discover, how many will be of classes of objects not yet seen at all? It will be truly amazing."
Quasars are intensely luminous objects at the farthest reaches of the visible universe. They are believed to be powered by the energy released by stars, dust and gas as they are drawn in and crushed by the gravity of super-massive black holes. They shine with the brilliance of more than 100 galaxies, from a volume of space no larger than our solar system.
Because they can be seen at such enormous distances, quasars offer astronomers a glimpse of the universe as it existed in its earliest years. Scientists aren't sure how quasars first formed. But by observing them at various distances, they hope to see how they evolved to their dimmer counterparts of more recent times.
At increasingly greater distances, Szalay said, astronomers are discovering fewer and fewer quasars, "which reflects the fact that we are seeing objects in the universe as it was first forming. The rest of them haven't formed yet."
By counting the number of quasars that existed at various distances and times, he said, we can understand "how the structures in the universe built up." The $80 million Sloan Digital Sky Survey is a five-year venture by government and university scientists to produce a three-dimensional digital map of 200 million objects across one-quarter of the sky.
The system, which won't complete its shakedown until next month, employs two telescopes, a spectrograph and a complex digital camera at the Apache Point Observatory in New Mexico.
Observational data are sent to the Fermi National Accelerator Laboratory in Chicago for computer processing and analysis. Scientists expect Sloan eventually will yield 40 trillion bytes of astronomical data in five years. The database will be archived at Hopkins and made available to scientists worldwide.
Pub Date: 12/08/98