spacetoday.net: Astronomers discover small exoplanets

Posted: Wed, Sep 1, 2004, 11:04 AM ET (1504 GMT)
Gliese 436 exoplanet illustration (NASA)

Astronomers announced the discovery of two relatively small extrasolar planets on Wednesday, a find that may create a new class of small exoplanets. The two planets, orbiting the stars 55 Cancri and Gliese 436, are each about the size of Neptune, with masses of 14 to 21 times that of the Earth. The two planets each orbit their stars at distances of only 4-6 million kilometers, and astronomers said the planets are more likely agglomerations of rock and ice rather than gas giants like Jupiter. The discovery of the planet around 55 Cancri brings the number of exoplanets known to orbit that Sun-like star to four, the most for any star other than our own Sun. The planets were discovered using the same radial velocity technique used to find most exoplanets to date. Last week a European team announced the discovery of a similar-sized exoplanet, suggesting that these planets form a new class of Neptune-sized exoplanets. Astronomers said they expect to find dozens of such exoplanets over the next few years as they continue their efforts to find more Earth-like exoplanets.