September 19,
2005
Distant stars yield clues to Milky Way
Artist's conception: Planets sweep away a clearing in mass of dust surrounding a fledgling star. (NASA/JPL-Caltech) |
bservations made by a research team led by Dan Watson, professor of physics and astronomy, suggest that a pair of young, distant stars may offer a glimpse into the early beginnings of our own solar system.
The team used NASA's Spitzer Space Telescope to detect gaps ringing the dusty disks around the stars, tell-tale signs that gas-giant planets have formed there. The new findings in the September 10 issue of Astrophysical Journal Letters not only reinforce the idea that giant planets like Jupiter form much faster than scientists have traditionally expected, but also indicate that one of the gas-enshrouded stars, called GM Aurigae, is analogous to our own solar system. At a mere 1 million years of age, the star offers astronomers a glimpse into the infancy of our world.
"GM Aurigae is essentially a much younger version of our Sun, and the gap in its disk is about the same size as the space occupied by our own giant planets," says Watson, who leads the Spitzer IRS Disks research team that includes astronomers from the University and seven other schools. "Looking at it is like looking at baby pictures of our Sun and outer solar system," he says.
The "baby planets" live within the clearings they have scoured out in the disks around the stars DM Tauri and GM Aurigae, 420 light years away in the Taurus constellation. These disks have been suspected for several years to have central holes that might be due to planet formation. The new spectra, however, leave no doubt: The gaps are so empty and sharp-edged that scientists say planetary formation is by far the most reasonable explanation for their appearance.
The new planets cannot yet be seen directly, but Spitzer's Infrared Spectrograph (IRS) instrument clearly showed that an area of dust surrounding certain stars was missing, strongly suggesting the presence of a planet around each.
"The results pose a challenge to existing theories of giant-planet formation, especially those in which planets build up gradually over millions of years," says Nuria Calvet, professor of astronomy at the University of Michigan and lead author of the paper. "Studies like this one will ultimately help us better understand how our outer planets, as well as others in the universe, form."
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