'Failed planet' intrigues UA astronomers

Astronomers at the UA's Steward Observatory found striking parallels to our own solar system in the debris of a "failed" planet around a nearby pair of stars.

Scientists believe the material would have become an Earth-like planet, had it successfully formed.

A wide band of rock particles was detected orbiting the star system HD 98800B, said Frank Low, a University of Arizona regents research professor emeritus of astronomy.

The celestial sandstorm was discovered using the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer.

The band of dust is similar to one found in the asteroid belt between Mars and Jupiter.

"I started looking for something like this for 30, 40-some years ago," Low said.

The asteroid belt would have formed a planet, but Jupiter's massive gravitational pull disrupted its development.

Low found the dust band in the asteroid belt in 1983 using NASA's Infrared Astronomical Satellite.

He was struck by the similarity between the material in the asteroid belt and that found around the stars.

The debris orbits the stars at a distance of 418 million miles, the same distance of the asteroid belt from the Sun. The belts of dust are also similar in composition.

Unlike our own solar system, which has only one sun, HD 98800B is a binary system in which two stars orbit each other.

Constantly shifting gravitational forces between the stars prevented the material from coalescing into a planet.

Low said that such systems are quite common in the galaxy.

"We're unusual in that we're a single, solitary star with a bunch of planets around it," he said. "The harder you look (at a star) the more likely you are to find a companion."

Low believes the two stars formed about 5 million years ago, making them mere youngsters compared with our own sun, which is 5 billion years old.

The find is significant not only because of the similarity with our own asteroid belt, but also because the material would have formed a rocky planet similar to Earth. Most planets found around other stars are giant balls of gas similar to Jupiter but far more massive.

If the material had formed a planet, it would have been a little more than half the size of Earth, Low said.

Dean Hines, a research associate who worked with Low on the project, said that a new space telescope may be able to find more failed planets.

The Space Infrared Telescope Facility, scheduled to be launched in 2001, will be "much more sensitive than IRAS was," he said.

Part of the satellite's imaging equipment is being designed and built at Steward Observatory under the direction of George Rieke, a UA astronomy professor.

The results of their work will be published in Astrophysical Journal Letters next month, he said.