spacetoday.net: Astronomers find 28 new exoplanets

Posted: Wed, May 30, 2007, 6:45 AM ET (1045 GMT)
Gliese 436b exoplanet illustration (L. Cook)

A team of astronomers announced this week the discovery of an additional 28 extrasolar planets as well as additional information about one previously-known intriguing world. The 28 new exoplanets, announced Monday at an American Astronomical Society conference in Honolulu, were found by two separate efforts in the Northern and Southern Hemisphere, both looking for periodic Doppler shifts in the spectral lines of stars caused by gravitational wobbles induced by orbiting planets. The discoveries bring the total number of known exoplanets to 236. The team also announced studies of a previously-discovered exoplanet, Gliese 436b, which recent research suggested may be made of "hot ice". They measured the size and density of the planet through a series of transits and found it has a density of two grams per cubic centimeter, suggesting a composition evenly split between rocky material, likely in the planet's core, and water, compressed into an ice mantle.