NEW YORK (Sep 11, 1996 5:36 p.m. EDT) -- 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 Thursday'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 be failed stars called brown dwarfs instead.
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.
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