Originally created 06/07/01

Asteroid belt around star resembles Earth's solar system at birth



PASADENA, Calif. -- Astronomers have found a star they believe is ringed by a massive belt of asteroids that resembles Earth's solar system at its birth, when a disk of dust and gas orbiting the sun first began to clump together to form planets.

Although the asteroids were not detected directly, the presence of a large amount of dust suggests that objects within the belt must be continually colliding to replenish the swirling disk of debris.

And with each collision, the objects are thought to be capable of merging to form larger and larger bodies and, eventually, planets. A similar process led to the formation of Earth's solar system.

"The existence of it points out maybe planets have formed or maybe they're being formed," said Christine Chen, a graduate student at the University of California at Los Angeles.

Chen and her adviser, Michael Jura, presented their research Monday at the 198th meeting of the American Astronomical Society.

Astronomers have found dust rings surrounding many hydrogen-burning stars. In the case of Zeta Leporis, however, Jura said the ring is closer to its parent star and warmer than other examples, leading them to speculate that it may resemble Earth's nascent solar system when it was just a few tens of millions of years old.

"It's probably more similar to our early solar system than other systems that have been observed," Jura said.

Chen and Jura used the W.M. Keck Observatory atop Mauna Kea in Hawaii to observe the star, which lies about 70 light years from Earth in the constellation Lepus.

The star's relatively young age - about 100 million years, compared to the Earth's 4.5 billion years - provided a strong clue that asteroid-sized bodies orbit in its ring of dust. Dust in orbit around a star is fairly unstable, lasting a fleeting 20,000 years before it spirals inward. Given the age of the sun, and the presence of a large amount of dust grains, some process must be at work to replenish the supply, Chen said.

"They must be generated through some secondary process," she said.

Mark Sykes of the University of Arizona's Steward Observatory called the findings "very, very interesting." He added that the system may already include a planet perhaps the size of Jupiter. The planet, Sykes said, would "pump up" the orbits of the much smaller asteroids, promoting more dust-producing collisions.

Chen and Jura said future observations could confirm their findings, as well as determine the composition of the ring.

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