Magazine article Science News

New Dust Sheds New Light on Planetary Birth

Magazine article Science News

New Dust Sheds New Light on Planetary Birth

Article excerpt

Astronomers once thought that planets could be born of only a single star. Now, researchers have discovered a disk-shaped layer of dust orbiting a mature binary star system-evidence that planets could have two or more stellar parents.

If other astronomers confirm the disk's existence, the number of possible planets in the galaxy could double, since more than half of the stars in the galaxy are part of binary or multiple systems.

Working at optical wavelengths, astronomers had previously spotted just one dust disk orbiting a mature star, Beta Pictoris, says Paul Kalas of the Max Planck Institute for Astronomy in Heidelberg, Germany. For some years, Kalas and David Jewitt of the University of Hawaii in Honolulu have been searching for other optically visible disks. In 1995, they found a second such disk. Their report appears in the March 6 Nature.

Visible dust disks survive for only a short period during a star's lifetime, says Kalas. When an inward-collapsing cloud of matter first shapes a star, it also gives rise to a disk. In turn, the disk begets small bodies called planetesimals, which can later cluster together through gravitational attraction and eventually grow into comets, asteroids, or planets.

The disks orbiting young stars can only be seen through an infrared telescope, which reveals the heat absorbed by the dust particles. Such telescopes tell astronomers little about the shape of the disk, however. That information is crucial because only thin, dense disks support planet formation. …

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