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Both planets are composed almost entirely of water;
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Half the planets must be made of something lighter than rock and heavier than hydrogen;
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It is likely that the planets are so hot that water immediately turns to steam.
Researchers I found two planets which are composed almost entirely of water, with a completely different formation than anything ever seen in our solar system. This is the first time astronomers have observed bodies of this size that can be confidently identified as aquatic worlds.
“We used to think that planets slightly larger than Earth were big spheres of metal and rock, like enlarged versions of Earth, which is why we call them super-Earths,” said Björn Benneke, one of the scientists on the study and a professor of astrophysics at the l University of Montreal.
“However, we have now shown that these two planets, Kepler-138c and ed, are quite different in nature: a large fraction of their entire volume is likely to consist of water. It’s the first time we’ve observed planets that can be reliably identified as waterworlds, a type of planet that astronomers have theorized to exist for a long time.”
Scientists haven’t directly detected the water, and it remains elusive at such a long distance. But research has shown that up to half of the planet should be made up of something lighter than rock and heavier than hydrogen, and the likeliest candidate for that material is water.
The two planets orbit the star Kepler-138, which is located in the constellation Lyra. They are three times the volume of Earth and twice the mass, but are much less dense than our planet.
Scientists warn that aquatic worlds are nothing like the classic planet we might imagine, with a surface area mostly similar to our Earth’s oceans. Instead, the planets are likely to be so hot that water immediately turns to vapor, creating a thick, dense atmosphere that can hide liquid water.
The planets are also outside the habitable zone, as they are too hot for liquid water and likely inhospitable to life. But new research has also found one more planet in the system, known as Kepler-138e, which is in the habitable zone.
