Dusty disks may slow down fast-spinning stars

From: http://edition.cnn.com/2006/TECH/space/07/24/space.stars.picture.reut/index.html

Monday, July 24, 2006 Posted: 2008 GMT (0408 HKT)

This artist's concept shows a dusty planet-forming disk in orbit around a whirling young star.

WASHINGTON (Reuters) -- When you're young and single, it's easy to dance fast. But when little ones are on the way, the dance tends to slow down. And so it seems to be with stars and the planet-forming disks that orbit them.

Scientists have long reckoned that the disks of gas and dust that can turn into planets might be putting the brakes on young stars, which can spin around in half a day or less if nothing tugs on them, researchers said on Monday.

"We knew that something must be keeping the stars' speed in check," Luisa Rebull of NASA's Spitzer Science Center said in a statement. "Disks were the most logical answer, but we had to wait for Spitzer to see the disks."

The orbiting Spitzer telescope sees the cosmos through infrared radiation, which makes it particularly good at finding the disks that swirl around stars, because the dust in the disks is heated by starlight and glows in infrared light.

Astronomers theorize that the disk slows the spinning star by pulling on its magnetic fields. When these fields pass through a dust disk, they are believed to get stuck "like a spoon in molasses," the researchers' statement said.

Stars start out as collapsing balls of gas that spin faster as they shrink; as they spin, excess gas and dust flattens around them into pancake-like disks.

Astronomers believe this gas and dust eventually clumps together to form planets.

Rebull was the lead author of a paper published in the July 20 edition of the Astrophysical Journal.