Distant gas cloud hints at early starbirth.

Which came first: the birth of stars or the formation of galaxies? Without any evidence of gas molecules--a signature of starbirth -- in a region distant enough to shed light on such early times, theorists have been left to speculate about this fundamental question. But new observations have dramatically narrowed the information gap -- and they hint that the stars predate the galaxies.

Peering back in time at a young galaxy near the edge of the observable universe, two researchers have found a massive carbon monoxide coud 10 times more distant than any molecular gas cloud previously detected. Their discovery, reported in the December ASTRONOMICAL JOURNAL, confirms a theory that the earliest glimmers of starbirth occurred just a few billion years after the Big Bang.

The violent explosion that most researchers believe sparked the expansion of the universe produced only two elements -- hydrogen and helium. The massive stars that condensed from clumps of these primodial gases end their lives in supernova explosions, spewing much heavier elements, such as oxygen and carbon, into the intersteller medium. And whether or not such an early generation of stars predates galaxies, this material eventually gets recycled into future generations.

In the new study, Robert Brown and Paul Vanden Bout of the National Radio Astronomy Observatory in Charlottesville, Va., have found compelling evidence that carbon and oxygen existed early in the history of the universe. The intense, millimeter-wavelength emissions they detected came from an enormous quantity of carbon monoxide. The observed emissions left the distant cloud about 12 billion years ago, when the cosmos had reached only 17 percent of its current age, the astronomers say.

Brown and Vanden Bout initiated their survey after hearing about an intriguing discovery. In the June 27 NATURE, researchers who had recently observed several celestial bodies viewed in 1983 by the Infrared Astronomical Satellite reported they had found a remarkable object: a distant, irregular blob--possibly a galaxy in the throes of creation -- emitting a powerful far-infrared signal. The object's enormous infrared luminosity--trillions of times that of our sun-indicated an abundance of dust. And where there's dust, Brown and Vanden Bout reasoned, there should be an even greater abundance of molecular gases -- especially if starbirth fuels the infrared emissions.

The two astronomers conducted their search in July, using a 12-meter telescope atop Arizona's Kitt Peak. "The strength of the carbon monoxide signal we detected indicates that the galaxy, while still young, has already seen the birth and death of the first generation of stars," Brown says. Taking the view that the amorphous object represents a galaxy still under development, he says the new observations suggests that stars form before galaxies. The work also suggests that preexisting gas clouds drawn together by gravity may represent the primal soup from which galaxies arise.

Brown and Vanden Bout's findings indicate that galaxies may have begun forming about 12 billion years ago, says Charles J. Lada of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. The vast quantity of carbon monoxide in the newly detected gas cloud -- more than 100 times the mass of the Milky Way -- further hints that this starbirth region may eventually develop into a cluster of galaxies, Lada says. Additional studies of the cloud and its environs may help astronomers piece together the shared early history of several different galaxy types, says Brown.

He and Vanden Bout detected other carbon monoxide emissions from the same cloud in October, using a telescope in Spain. This follow-up study, he says, confirms the existence of molecular gas in the distant cloud.