Planet Hatchery

Monday, December 01, 1997
In the past couple of years astronomers have found indirect but convincing evidence of planets around distant stars--the gravitational pull of these invisible planets makes their parent stars wobble. Now researchers at Caltech have found what appears to be a solar system in the making about 450 light-years away in the constellation Auriga.

While surveying young, large stars in nearby parts of our galaxy with an array of radio telescopes, Caltech astronomer Vincent Mannings detected a smear of cool gas and dust around a hot, young star known only as mwc 480. It could be a construction site for asteroids, he says, and maybe for planetary cores as well.

The disk, which weighs about as much as 40 Jupiters and is about ten times as wide as our solar system, is not the first to be discovered. Astronomers know of at least six others. But the new disk in Auriga is unique in at least two respects. This is the clearest evidence we have of a rotating disk around a young star, says Mannings, who detected the rotation by observing slight differences in the wavelengths coming from opposite sides of the disk.

The second difference, he notes, is that mwc 480 is much larger than the other stars that have been found to have disks around them. This star is three times as massive as most stars, he says. But perhaps the disk’s most interesting feature for astronomers is that it appears to be a younger version of one found a few years ago around a star called Beta Pictoris.

Beta Pictoris is about 20 times older than mwc 480, he says. It has around it a very tenuous disk of dust grains. The disk around mwc 480 is much thicker, possibly because it hasn’t been swept clean by the formation of planets. We think this disk looks similar to the disk that was around our sun, says Mannings. It seems to have the right sort of properties and the right amount of mass.
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