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.
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.
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.