It’s a soupy, steamy sauna, smaller than Uranus but bigger than Mother Earth.
Right out of central casting, planet GJ 1214b “is like no planet we know of,” astronomer Zachory Berta of the Harvard-Smithsonian Center for Astrophysics (CfA) said on Tuesday in a NASA statement. “A huge fraction of its mass is made up of water.”
This waterworld, as it has been dubbed, was discovered in 2009, and water was suspected in its atmosphere. In 2010 CfA scientist Jacob Bean and his colleagues measured the atmosphere and determined that it may very well be composed mainly of water. But there were other explanations, such as haze surrounding the planet, so they could not say for sure.
However, now Berta and colleagues including Derek Homeier of ENS Lyon, France, have studied it through the Hubble telescope as it passed in front of its sun, filtered the star’s light through the planet’s atmosphere and allowing them to analyze its composition. That indicated water vapor.
Density calculations showed it to have more water than Earth does, and much less rock, NASA said, and on February 21 the space agency announced it had found a planet covered almost completely in water.
“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.
In other words it doesn’t really look like the 1995 movie Waterworld starring Kevin Kostner.
GJ 1214b is 2.7 times Earth’s diameter and weighs seven times as much, NASA said. It is 1.2 million miles from its sun, a red dwarf, which it orbits every 38 hours.
The theory, NASA said, is that GC 1214b must have formed at a more distance orbit from the star in a place where water ice was available. Then it drifted in closer early on, as the system evolved. That would have sent it through the habitable zone of the star, with surface temperatures would be similar to Earth’s.
“How long it lingered there is unknown,” NASA said.