Light from the first stars launches a new astronomy

After several decades of speculation, astronomers have glimpsed the shadows of the very first atoms, cast in the light of the earliest stars. Yet as significant as this discovery is, it represents only the beginning of what some scientists call "the new astronomy."

Astronomers working in this new mode will no longer scan the skies directly. Instead, they will pursue cosmic questions by searching vast databases assembled by instruments whose only goal is to garner as much information as possible about every object they can detect.

The first such database - the Sloan Digital Sky Survey - is a collaborative effort that has developed over the past 12 years among some 100 scientists at 11 institutions in Germany, Japan, and the United States. Funds from the Sloan Foundation, several US government agencies, and the collaborating institutions support it. When the survey is completed in three to four years time, instruments at Apache Point Observatory in New Mexico should have recorded the brightness, color, and shape of 100 million objects plus the distances to a million galaxies and 100,000 quasars over one-quarter of the sky.

Quasars are very compact, very bright objects that can outshine a whole galaxy of ordinary stars. One of these cosmic power houses now has produced the survey's first fruits. Survey scientist Xiaochui Fan at the Institute for Advanced Study in Princeton and several colleagues have used early survey data to locate the most distant quasar yet found. The light we now see from it left its source at the end of what astronomers call the universe's Dark Ages.

The first atoms of hydrogen and helium appeared about 300,000 years after the universe emerged in an outburst of energy 12 billion to 15 billion years ago. What happened over the next half-billion years before the first stars and quasars lit up has been a tantalizing mystery. Now cosmologist Robert Becker at the University of California in Davis, Dr. Fan, and some other survey colleagues have used that distant quasar to probe this mystery.

Studying its light with one of the world's most powerful telescopes - the Keck instrument on Mauna Kea in Hawaii - they find the imprints of primordial atoms. These atoms absorb certain wavelengths of the quasar's light, casting shadows so to speak across the light's spectrum. Besides the original hydrogen atoms, there are traces of carbon, nitrogen, oxygen, and silicone cooked up in the first stars. In the Aug. 3 announcement, Dr. Becker says that "these observations provide our first glimpse at truly primordial material." Without the database to find the crucial quasar, that glimpse would not have occurred.

The new astronomy involves more than building databases. It requires an arsenal of some of the most complex computer programs ever written to process, organize, analyze, and communicate the information. This is as challenging as the Human Genome Project. That project has transformed the way biologists do basic research.

Sloan survey scientists predict that their work will likewise begin to transform the way astronomers pursue their ancient quest.

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