ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Thursday, September 12, 1996 TAG: 9609130019
SECTION: NATIONAL/INTERNATIONAL PAGE: A-8 EDITION: METRO
DATELINE: NEW YORK
SOURCE: Associated Press
ASTRONOMERS once believed planets were rare. Recently, they've had to revise that view.
After a year in which scientists discovered several apparent planets outside the solar system, a new analysis concludes that folks, you ain't seen nothin' yet.
Hidden planets may be lurking around half the Milky Way galaxy's 100 billion stars, the analysis suggests.
``We'll see an explosion'' in planet discoveries, said researcher Steven Beckwith of the Max Planck Institute for Astronomy in Heidelberg, Germany.
He presented the evidence for his optimism in today's issue of the journal Nature with Annelia Sargent of the California Institute of Technology in Pasadena.
Scientists want to find distant planet systems not only for the tantalizing possibility of finding life, but also to test theories of how the solar system formed.
There's no direct way to tell now how many ordinary stars like the sun have planets.
For years, astronomers have believed planets were rare. But the rush of reports in the past year has encouraged the belief that they are quite common, and Beckwith's 50 percent estimate fits in with that thinking, said Steve Maran, assistant director of space sciences at the Godddard Space Flight Center in Greenbelt, Md.
Not everyone is guessing that high. David Black, director of the Lunar and Planetary Institute in Houston, said he wouldn't be surprised if the answer turned out to be 10 percent.
Since last fall, at least eight stars have been found to have a telltale wobble that suggests they're being pulled around by orbiting planets. Some researchers maintain, however, that at least some of these orbiting bodies may instead be failed stars called brown dwarfs.
In the Nature article, Beckwith and Sargent analyze previous studies to argue that a lot more planets are out there. They note that in several regions of the cosmos, half or more of very young stars show signs that they're surrounded by disks of gas and dust that look like the forerunner of the solar system.
Scientists believe that when the sun was young, a disk of gas and dust surrounded it like a huge spinning pizza. Dust in this disk started to clump up, and some of these clumps grew into planets.
In all, it took maybe 10 million to a few hundred million years to build the solar system's planets, which sucked up material from the disk.
``If you look at other stars, you have evidence of enough material and enough time and the right conditions to make planetary systems,'' Beckwith said in a telephone interview.
LENGTH: Medium: 58 linesby CNB