Scientists find new ‘waterworlds’ that look nothing like any planet in our solar system
Scientists have found two “water worlds” that are unlike anything seen in our solar system.
The planets are almost entirely made up largely of water, marking the first time that such worlds have ever been confidently identified by scientists.
Previously, the researchers were thought to be far more standard planets – but they are actually far more pioneering than we realised, scientists say.
“We previously thought that planets that were a bit larger than Earth were big balls of metal and rock, like scaled-up versions of Earth, and that’s why we called them super-Earths,” said Björn Benneke, one of the scientists on the new research.
“However, we have now shown that these two planets, Kepler-138c and d, are quite different in nature: a big fraction of their entire volume is likely composed of water. It is the first time we observe planets that can be confidently identified as water worlds, a type of planet that was theorized by astronomers to exist for a long time.”
Scientists have not directly detected the water, and that remains difficult at such a long distance. But investigation showed that up to half of the planet should be made up of something lighter than rock and heavier than hydrogen – and the most likely candidate for that material is water.
The two planets are in orbit the star Kepler-138b, which is 218 light years and situated in the Lyra constellation. They have volumes three times that of Earth, and masses twice as big – but are much less dense than our own planet.
Scientists caution that the water worlds do not look like the classic planet we might imagine, with a surface primarily like the oceans on our Earth. The planets are instead likely to be so hot that the water will immediately turn to steam, creating a thick and dense atmosphere that may hide liquid water.
The findings are described in a new paper, ‘Evidence for the volatile-rich composition of a 1.5-Earth-radius planet’, published in Nature Astronomy.
