Solar Dust Rings Mark the Building Blocks of Planets

For the first time, scientists have found rings of dust around planet-bearing stars -- an important confirmation of theories about how planets form, NASA announced Thursday.

The Spitzer Space Telescope found the rings around five stars about the size and age of 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 the 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 was unclear whether that was 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 might help researchers know where to look as they continued to hunt for planets outside our solar system.

NASA also announced that the Hubble Space Telescope found dust rings around two stars that were 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 gaps in their centers where planets may have swept up the debris; actual planets have not been confirmed.