Big Stars Get Dusty Too

Scientists have discovered a dust ring around a hot, massive star--raising the possibility that planets might exist around giant stars. The tentative finding, which remains unpublished and unconfirmed, could explain how such stars get so big in the first place.

Stars are born when gas collapses into a ball dense enough to trigger nuclear reactions. Smaller stars like our sun are often surrounded by a veil of gas and dust that can clump together to form planets. Massive stars, on the other hand, send out such intense radiation that they blow away nearby material. But one star has for awhile loomed as a possible exception to the rule: Several years ago, radio observations hinted at a dust disk surrounding a star, known as G339.88-1.26, that is 20 times more massive than the sun and pumps out 10,000 times more radiation, mainly ultraviolet.

A team of astronomers with the European Southern Observatory in Garching, Germany, found the disk by the signature infrared rays that dust emits after it absorbs UV rays. Because of the absorption, the dust particles don't get blown away and will shield the gas. This could allow the star to continue accreting matter, says Hans-Ulrich Käufl, an astronomer with the team. Whether planets could coalesce near such a hot star is still open to question, Käufl adds. To find out, he says, they will have to look at the 100 to 150 massive stars that may have dust rings.

A dust ring around so massive a star is extraordinary, says Charles Telesco, an astronomer at the University of Florida, Gainesville. "It's a very exciting object," he says, adding that if it is confirmed it "will be a breakthrough in our understanding" of dust discs around stars. Telesco's group plans to take a look for themselves next week, with the National Oceanic and Atmospheric Administration's 4-meter telescope in Cerro Tololo, Chile.