Thursday, September 24, 1998 Published at 14:22 GMT 15:22 UK
New planets' star roll
Paul Butler and Geoff Marcy ,co-discoverers of the new planets
Two new worlds circling two nearby stars have been discovered. Our science editor Dr David Whitehouse explains
One of the new planets is a remarkable world seared by the heat of its parent star.
Larger than Jupiter, it would appear as a world covered in deep blue-violet clouds as it skims the outer atmosphere of its parent yellow star every three days.
The discovery is the first planet discovered that orbits its star at the Earth-Sun distance.
"We have discovered planets that orbit much closer and further from their stars than the Earth-Sun distance," said Professor Geoffrey Marcy, of San Francisco State University.
"We wondered if nature rarely puts planets at one Earth-Sun distance. Now we know that such planets are not rare," he added.
The new worlds were found duing a survey of nearby stars using the Keck telescope in Hawaii.
They were discovered by detecting a characteristic wobble in the motion of the star. This is caused by the gravitational effect of the planet's orbit.
Since 1995, 12 planets orbiting other suns have been found. It means astronomers now know of more planets around other suns than in our own solar system.
As the survey continues Marcy expects to discover up to 24 Jupiter-sized planets orbiting their stars at the Earth-Sun distance.
As yet their technique is not sensitive enough to detect Earth-sized planets circling other stars.