Spying on Solar Systems in the Making

Astronomers today unveiled unprecedented views of swirling disks of dust around young stars, apparently the nurseries of planets like our own. The new images, made with sensitive new midinfrared and submillimeter detectors, show several disks with mysterious bulges that may be dust-cloaked giant planets and others with holes torn in them, apparently by newborn planets. In one case--the youngest disk ever seen around a full-grown star--astronomers may be spying on the very moment of planet birth.

One set of images, of the stars Vega, Fomalhaut, and Beta Pictoris, comes from a British-American team led by Wayne Holland of the Joint Astronomy Center in Hawaii and Benjamin Zuckerman of the University of California, Los Angeles. Fifteen years ago, satellite observations had shown that these three stars (and a handful of others) emit more infrared radiation than expected, probably because they are ringed with disks of warm dust. Now the team has used a submillimeter telescope on Mauna Kea, Hawaii, to capture intimate views of all three stars. The images, which will appear in Thursday's Nature, reveal the mysterious bright blobs around Vega and Beta Pictoris and a gap in the Fomalhaut disk. The missing dust, says Holland, "might have formed rocky planets like Earth."

The stars that host those disks are all several hundred million years old--well past prime planet-forming age. But Ray Jayawardhana of the Harvard-Smithsonian Center for Astrophysics and his colleagues have used a midinfrared camera on a 4-meter telescope in Chile to see a flattened dust disk around a much younger star called HR4796A. At a mere 10 million years old, the star is a "perfect [age] for planets to be forming in its disk," says Jayawardhana. A second team, from the California Institute of Technology and Franklin & Marshall College in Lancaster, Pennsylvania, has independently photographed the disk.

The holes and bulges in these images suggest that once a star has a dust disk, planets are likely to follow, says Rens Waters of the University of Amsterdam. "Apparently, it's not hard to make planets," he says. "As soon as a star is surrounded by a disk of gas and dust with the right density and composition, you end up with a solar system."

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