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Hubble's 'waterworld' discovery: A new type of planet

Essentially one big ocean, GJ 1214b orbits a red dwarf star in this artist's conception. Researchers now believe the "water world" represents an new type of planet.David A. Aguilar, CfA

NASA’s Hubble Space Telescope has confirmed the existence of a completely new type of planet.

By analyzing the previously identified world GJ 1214b -- an Earth-like superplanet located outside of our solar system -- astronomer Zachory Berta and his team have discovered a strangely unique water-based planet.

When it comes to planets, our solar system contains three distinct types: rocky and terrestrial like Mars and Earth, gas giants such as Jupiter and Saturn, and ice giants like Uranus and Neptune.

GJ 1214b, researchers soon realized, was none of the above.

“GJ 1214b is like no planet we know of,” said Berta, who hails from the Harvard-Smithsonian Center for Astrophysics. “A huge fraction of its mass is made up of water.”

“If you want to describe in one sentence what this planet is, it’s a big, hot ocean,” Harvard University astronomer David Charbonneau told Wired in 2009 when the planet was first discovered by the MEarth Project, an NSF-funded, robotic observatory in Arizona.

It might have life, but it would have to be a strange kind of life.

- Harvard astronomer David Charbonneau

Since the planet is too far to be seen directly, researchers have had to infer its presence and characteristics from subtle distortions in light. As such, Berta and his crew have only recently been able to determine the planet’s steamy atmosphere.

“We’re using Hubble to measure the infrared color of the sunset on this world,” Berta explained. He found the spectrum of GJ 1214b to be featureless across many colors, a model consistent with a dense atmosphere composed of water vapor.

“The Hubble measurements really tip the balance in favor of a steamy atmosphere,” he said.

The result is a water world very different to our own, one where the atmosphere is roughly ten times thicker creating extreme atmospheric pressures with little light getting through.

“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.

Life too, if it exists, will certainly be weird.

“I don’t want to imply that there’s any indication of life as we know it. It might have life, but it would have to be a strange kind of life,” Charbonneau told Wired.

“This planet will occupy us for years. That’s part of what’s so exciting about it.”