By Ron Cowen
NANTES, France — Astronomers have discovered the first known system around a distant star with three planets categorized as superEarths.
The three extrasolar planets, all presumably rocky, range in mass from 4.2 to 9.4 times that of Earth. They orbit a star called HD 40307 just 42 light-years from Earth. HD 40307 has a mass about 80 percent that of the sun.
Although the planets all lie too close to their parent star to support life, the finding bodes well for ultimately finding a true twin of our planet, says Stephane Udry of Geneva Observatory in Switzerland, a member of the discovery team. Veteran planet hunter Michel Mayor of Geneva Observatory announced the discovery on June 16 at a conference on superEarths in Nantes, France.