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Scientists reveal nine new planets

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Scientists are able to detect new planets because of their gravitational pull on stars  

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Giant planets

Unusual orbit

Further analysis

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MANCHESTER, England -- Astronomers have revealed details of nine previously unknown planets orbiting stars relatively close to Earth.

They include only the second multi-planetary system ever found and bring the total number of known planets circling stars other than our own sun to 50.

Details of the discoveries were being made at the International Astronomical Union (IAU) General Assembly, in Manchester.

Five of the new planets were detected by astronomers based in Geneva, Switzerland, using information from the European Southern Observatory's La Silla observatory in Chile.

Giant planets

None of the planets have ever been seen by humans, but scientists know they exist because of the gravitational pull they exert on the stars they orbit and the subsequent detectable effect they have on the light the stars emit.

The new multi-planet system consists of two Saturn-sized gaseous giant planets, HD 83443 b, which the scientists said they detected in May, and HD 83443 c, which they have just discovered.

The planets circle the HD 83443 star, which is 141 light years away from our solar system in the Vela constellation.

Until now, only one other extra-solar multi-planetary system -- three planets around the Upsilon Andromedae star -- had previously been detected.

The Geneva team also discovered planet HD 190228, which is 203 light years away and was found using information gathered at an observatory in Haute-Provence, France.

In separate discoveries, a team of scientists based at the University of California, Berkeley, U.S. said they had found three new planets, all gas giants similar to Jupiter.

Unusual orbit

They have also discovered a planet orbiting the star Epsilon Eridani which could provide answers to questions about the existence of life on other planets.

Dr. William Cochran of the University of Texas' McDonald Observatory said: "Detecting a planet orbiting Epsilon Eridani -- a star very near to our own sun -- is like finding a planet in our own backyard."

Geoff Marcy, a University of California professor, said that while most of the planets in our solar system move in nearly circular orbits, the new planet at Epsilon Eridani has an oblong orbit, as do most of the other newly discovered planets.

Earth's circular orbit provides a relatively stable environment that balances out the extremes of cooling and heating experienced on the surfaces of planets with oblong orbits.

Marcy said: "It may be that life here is possible because of the circular orbit.

"It's a very exciting discovery because ... the star itself is the closest star for which a planet has ever been discovered," he added. "It's only 10 light years away. In the next 100 or 200 years, it will be one of the first stars humans visit." he said.

Further analysis

In another discovery, the Berkeley scientists found that multi-planetary systems might be more common than was previously thought.

A study of 12 stars, which already had one planet circling them, has found that five of them have another planet orbiting them.

The scientists found that these stars had "wobbles" which could not be explained simply by the presence of the one planet.

"This is the first time anyone has noticed that such a high percentage of stars with one known planet show evidence of a second companion," Debra Fischer, one of the team, said.

"We found changes in the speed of stars that indicate that there is something pulling it around. But without further analysis it is unclear what that is."

The 11-day conference, which will be attended by 2,000 astronomers from 87 countries, is expected to include several other announcements of new planets having been discovered.

It will feature almost 500 talks, on subjects as diverse as searching for planets outside our solar system, the effects of the sun's activity on Earth's environment, space exploration and the structure and creation of the Universe.

Reuters contributed to this report.

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August 3, 2000

International Astronomical Union

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