Super-hot 'waterworld' is an entirely new class of planet

According to astronomer Zachory Berta, "GJ1214b is like no planet we know of." That's because a "huge fraction" of the planet is made up of water — a concept that's hard to drink in when one considers the fact that GJ1214b is a scant 1.3 million miles from its native star and boils at 450 ° Fahrenheit. It's unlike any other planet Hubble has spied to date.

We've known about GJ1214b for a while now. It was first spotted in 2009 by astronomers at the MEarth Project, which uses a group of terrestrial robotic telescopes to do its exoplanet hunting. Now that astronomers at the Harvard-Smithsonian Center for Astrophysics (or CfA) turned the Hubble Space Telescope's Wide Field Camera 3 toward GJ1214b for observation, we know even more.

It's a super-Earth about 2.7 times the diameter of Earth, weighs seven times as much and orbits its star every 38 hours thanks to that close-in orbit. It also appears to have a steamy atmosphere — something that was of particular interest to astronomers.

"GJ1214b is like no planet we know of. A huge fraction of its mass is made up of water," Berta, who works at the Harvard-Smithsonian Center for Astrophysics, said in a statement by CfA. He added, "The Hubble measurements really tip the balance in favor of a steamy atmosphere... 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."

To determine the atmospheric makeup of a planet 40 light years away, Berta and his team had to be creative. It was already thought that GJ1214b's atmosphere was mostly water, but it wasn't known whether it was a light haze or a thicker, steamier soup. Using Hubble, Berta and co. saw that "light filtered through the planet's atmosphere" when it passed before its star. Now, the astronomers think a steamy mix of gases best describes GJ1214b's atmosphere.

It won't be a planet humanity can go and colonize. Well, unless some of us start growing gills. It does represent a new planet class, however. In our solar system we have rocky, gassy and icy planets. GJ1214b, which is believed to be predominantly water, would be a fourth type if verified.

More details about GJ1214b and other exoplanets will undoubtedly come once there's a next generation telescope in place such as the James Webb Space Telescope.

CfA, via ESA/Hubble, via Pop Sci

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