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Berkeley Astronomers Find Nearby Stars Where Planets May Be Forming

By Robert Sanders, Public Affairs
posted September 2, 1998

Berkeley space scientists have found two nearby stars -- each about 450 light years from Earth -- that appear to be continually bombarded by comets.

Because it is believed that planets coalesce from the collision of comets and asteroids, it is likely that planets are forming within the gas and dust surrounding these stars.

"Observations of comet-like bodies, or 'planetesimals,' outside of our solar system are of great importance in understanding the role of comets in the formation of all planetary systems," said Barry Welsh, a researcher in interstellar gas studies. "Our observations indicate a high level of cometary activity in these disk systems, suggesting that there is potentially plenty of raw building material for new planetary bodies."

Welsh and Berkeley colleague Nahide Craig, and Ian Crawford of University College, London, England, who made the discovery in 1997 from the 1.5-meter telescope at Chile's Cerro Tololo Observatory, reported data on the two stars -- HD85905 and HR10 -- at a meeting of the American Astronomical Society held in San Diego in June.

Both stars show clear evidence of surrounding disks of gas and dust, Welsh said. Until recently, only the star Beta Pictoris was known to possess both proto-planetary dust and gas clouds.

"Our observations show large changes in the amount of gaseous calcium and sodium from night to night," Craig said. "The amounts seen are consistent with the evaporation of gas from comet-like objects, similar to the huge tails of glowing gas that many people in North America saw last year from Comet Hale-Bopp."

Crawford added, "Much attention has recently been focused on detecting the infrared signatures from disks of dust surrounding proto-planetary systems. Our new observations show the presence of gas disks and comet-like bodies in these planetary building sites. Although the inner planets in our own solar system are made mostly of rock, the outer planets like Jupiter and Saturn are gas giants. Our new data show a potential reservoir of gaseous building materials for such planets."

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