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Tuesday, February 21, 2012

Astronomers Announce Discovery of "Watery" World

At seven times the Earth's mass, and with surface temperatures of over 400 degrees F, it's no Cachalot. From MSNBC:
Scientists have discovered a new type of alien planet — a steamy waterworld that is larger than Earth but smaller than Uranus.

The standard-bearer for this new class of exoplanet is called GJ 1214b, which astronomers first discovered in December 2009. New observations by NASA's Hubble Space Telescope suggest that GJ 1214b is a watery world enshrouded by a thick, steamy atmosphere.

"GJ 1214b is like no planet we know of," study lead author Zachory Berta of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said in a statement. "A huge fraction of its mass is made up of water."

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But GJ 1214b, which is located 40 light-years from Earth in the constellation Ophiuchus (The Serpent Bearer), is something new altogether, researchers said.

This so-called " super-Earth " is about 2.7 times Earth’s diameter and weighs nearly seven times as much as our home planet. It orbits a red-dwarf star at a distance of 1.2 million miles (2 million kilometers), giving it an estimated surface temperature of 446 degrees Fahrenheit (230 degrees Celsius) — too hot to host life as we know it.

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Since astronomers know GJ 1214b's mass and size, they're able to calculate its density, which turns out to be just 2 grams per cubic centimeter (g/cc). Earth's density is 5.5 g/cc, while that of water is 1 g/cc.

GJ 1214b thus appears to have much more water than Earth does, and much less rock. The alien planet's interior structure is likely quite different from that of our world.

"The high temperatures and high pressures would form exotic materials like 'hot ice' or 'superfluid water,' substances that are completely alien to our everyday experience," Berta said.

GJ 1214b probably formed farther out from its star, where water ice was plentiful, and then migrated in to its current location long ago. In the process, it would have experienced more Earth-like temperatures, but how long this benign phase lasted is unknown, researchers said.

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