Alien Planet: The Ultimate Water World

A planet orbiting a nearby star is the best candidate yet for an alien world made almost entirely of liquid water. The discovery suggests that “super-Earths” are a much more diverse bunch than we suspected.

Super-Earths weigh up to 10 times as much as our planet. They may be among the most common types of planet in the Milky Way, and some could turn out to be cosy places for life. Around a dozen have been found, but for the most part, astronomers have been unable to pin down their properties because they don’t pass in front of, or transit, their host stars as seen from Earth. Transits reveal a planet’s size, allowing its density and composition to be inferred.

Earlier this year, the CoRoT spacecraft found the first transiting super-Earth, called CoRoT-7b. Broiled by its host star, the planet may be a rocky body covered in pools of lava on the side that always faces the star.

Now, astronomers have found the second transiting super-Earth around a nearby red dwarf. Called GJ 1214b, it is about 19 times as large as Earth by volume but only 6.6 times as massive. [Read more]

Ivan Semeniuk, 16th December 2009, New Scientist: http://www.newscientist.com/article/mg20427394.000-alien-planet-could-be-ultimate-water-world.html