And the exoplanet count marches on. A few days ago astronomers announced they had found a handful of new planets around sun-like stars, some only 29 light years away. Now, in a study published today in Nature, a team led by David Charbonneau unveils a new super-Earth that’s hot, watery, and only 2.68 times the size of our own world.

The planet currently bares the name GJ 1214b, and while Charbonneau says it’s probably not habitable (because of the 400-degree Fahrenheit surface temperature), it’s not too far off the mark. Geoffrey W. Marcy, a planet hunter from the University of California, Berkeley, wrote in an accompanying article in Nature that the new work provided “the most watertight evidence so far for a planet that is something like our own Earth, outside our solar system” [The New York Times].

Despite the heat, the astronomers say, their new planet most likely holds a lot of water. By determining the new world’s mass and size as it passed in front of its star, the researchers could calculate its density: one-third that of Earth. Because water has a much lower density than rock, astronomers figured that the “most plausible scenario is a planet made mostly of water, with a significant atmosphere,” says Charbonneau. So despite its high temperature, GJ 1214b’s high atmospheric pressure and relatively low density mean liquid water could exist there after all [TIME].

Finding GJ 1214b didn’t take a giant telescope or a space observatory like NASA’s Kepler mission. The team used an array of smaller telescopes on an Arizona mountaintop, and project called MEarth. Relatively dim, relatively close stars were favored because the planet’s dimming effect would be more noticeable than it would be with brighter, bigger, farther-out stars [MSNBC]. One of Charbonneau’s graduate students noticed the blip as the planet passed in front of its star, and it didn’t take long to confirm the find: GJ 1214b orbits its M-dwarf star once every 38 hours.

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DISCOVER: How Long Until We Find a Second Earth?
DISCOVER: The Inspiring Boom in Super-Earths
DISCOVER: Space Scientist: Geoff Marcy and Paul Butler

Image: David A. Aguilar/CfA