Shedding light on a luminous galaxy.

Last year, British astronomers reported the serendipitous discovery of the brightest object ever observed in the universe --a distant galaxy that has an infrared luminosity more than 100 trillion times that of the sun at all wavelengths (SN: 6/29/91, p.406). At the time, co-discoverer Michael Rowan-Robinson of Queen Mary and Westfield College in London and his colleagues speculated that either a dust-shrouded quasar or powerful bursts of star formation could account for the galaxy's record-breaking brightness.

Two new studies appear to favor the star formation model. They suggest that light from massive, brightly burning stars, which are born and die at a furious pace, may fuel galaxies just as effectively as a quasar. But Eric E. Becklin, an astronomer at the University of California, Los Angeles, notes that such rapid-fire star production--the equivalent of 1,000 stars exploding as supernovas each year--"is way off the scale of star formation" detected in any other galaxy and may not represent the true nature of this infrared-bright body, dubbed IRAS F10214+4724.

Using a millimeter-wave radio telescope in Granada, Spain, Philip Solomon of the State University of New York at Stony Brook and his colleagues found that the infrared galaxy emits strong radio signals from carbon monoxide - a telltate sign of star formation. The strength of the signals indicates that most of the mass of this galaxy, unlike that of most known galaxies, consists of interstellar gas rather than stars.

Another team, which had previously detected carbon monoxide emissions, now reports that the galaxy emits radio signals from atomic carbon. Robert L. Brown and Paul A. Vanden Bout of the National Radio Astronomy Observatory in Charlottesville, Va., say their findings also hint that IRAS F10214+4724, as now viewed, represents a primeval galaxy in which some giant gas clouds are still collapsing to form stars and starbirth has only recently begun.

Rowan-Robinson says the jury is still out on the power source fueling the luminous body, which may lie some 13 billion light-years from Earth. Both starbirth and radiation from a dust-shrouded quasar may contribute significantly to the galaxy's infrared brilliance, he says.