Posted on 12/09/2004 7:27:19 PM PST by NormsRevenge
WASHINGTON (Reuters) - Planet-building is dusty work, and now two space telescopes have captured images of cosmic construction materials: disks of dust circling stars about the same size as our sun.
Pictures released on Thursday from NASA (news - web sites)'s Hubble and Spitzer telescopes give the clearest look yet at the early and late phases of the planetary construction process.
Most astronomers believe planets are created from the disks of dust and gas that form around young stars, and the younger the star, the bigger the dusty disk.
Big gas giant planets like Jupiter form first, then smaller rocky so-called terrestrial planets form later when the orbiting rocks collide and stick together.
The Hubble Space Telescope (news - web sites) managed to see a very young sun-like star -- a mere 50 million to 250 million years old -- with a big ring of potentially planet-forming dust around it.
This is old enough to form a gas planet, but probably too young to have produced an Earth-like rocky planet, scientists said in a telephone news briefing.
"Basically, it shows one of the possible pasts of our own solar system," Hubble astronomer David Ardila said.
Observations from the Spitzer Space Telescope indicate six middle-aged sun-like stars with much thinner dust disks around them. At about 4 billion years old, these six are almost as old as the sun.
Astronomers already knew these stars harbored planets, because they had been detected earlier by watching the characteristic wobble that the unseen planets' gravity produces in the stars they circle.
Spitzer was looking for dust disks around these stars, which in this case would be remnants of planetary construction.
In planetary systems of this age, these disks would be as much as 100 times thinner than those around a younger star, and therefore much harder to spot. But Spitzer's infrared detectors managed to find them by looking for unexpected warmth.
"In the case of six of these stars, we found that the amount of heat they're emitting is considerably in excess by factors of two to a factor of 15 times more heat than is expected from the surface of the star itself," Spitzer scientist Charles Beichman said at the briefing.
"These are really the first planet-bearing stars around which we've found disks of material analogous to our own Kuiper Belt," Beichman said. The Kuiper Belt is a ring of icy space rocks and rubble outside the orbit of Neptune.
More information and images are available online at http://hubblesite.org/news/2004/33.
In this photo from the Spitzer Space Telescope released by NASA (news - web sites), infrared images of six stars are seen. The yellow, fuzzy clouds are rings of dust like the one that surrounds our own Sun. The telescope found rings of dust around planet-bearing stars, an important confirmation of theories about how planets form, NASA announced Thursday, Dec. 9, 2004. (AP Photo/NASA/JPL)
http://news.yahoo.com/news?tmpl=story&u=/ap/20041209/ap_on_sc/building_planets_1
By ROBERT JABLON, Associated Press Writer
PASADENA, Calif. - For the first time, scientists have found rings of dust around planet-bearing stars — an important confirmation of theories about how planets form, NASA (news - web sites) announced Thursday.
The Spitzer Space Telescope found the rings around five stars about the size and age of the Earth's sun, which is about 5 billion years old. A ring or disc also was found around a sixth star only a few hundred million years old. All are orbited by gaseous planets.
One scientist compared Spitzer's discovery to finding bricks left over from construction of a house, since planets are believed to form out of dust clouds.
"It's a completion of our picture of the planet-formation process," Alycia Weinberger, an astronomer at the Carnegie Institution of Washington, said during a conference call.
"We really didn't know of any system that harbored both planets and discs other than our own solar system," Weinberger said.
No dust discs were seen around 20 other stars known to have planets, although scientists said it is unclear whether that is because they don't exist or because they glow too faintly with reflected light for Spitzer's infrared eye to detect.
Charles Beichman, a Spitzer scientist at NASA's Jet Propulsion Laboratory in Pasadena, said the discovery may help researchers know where to look as they continue to hunt for planets outside our solar system.
Our system has the Kuiper (KYE'-per) Belt, a disc of icy debris beyond the orbit of Neptune. Many comets come from there. The disc is relatively faint, however, and was discovered only about a decade ago.
Also Thursday, NASA announced the Hubble Space Telescope (news - web sites) found dust rings around two stars that are much younger and smaller than the sun, at 12 million years for one and 50 to 250 million years for the other. The rings had big gaps in their centers where planets may have swept up the debris, although actual planets have not been confirmed.
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In this artist's concept released by NASA (news - web sites), a ring of dusty debris is seen around a star. NASA's Spitzer Space Telescope found rings of dust around planet-bearing stars, an important confirmation of theories about how planets form, NASA announced Thursday, Dec. 9, 2004. (AP Photo/NASA/JPL)
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On the Web:
Spitzer Telescope: http://www.spitzer.caltech.edu
bttt for later read.
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