Astronomers discover strange twin planets might be water worlds

[Judi Lynn]

By Meghan Bartels
published about 19 hours ago

Two planets found by NASA's retired Kepler Space Telescope may be made mostly of water, according to new research.

The two exoplanets, dubbed Kepler-138c and Kepler-138d, orbit a star located about 218 light-years away from Earth in the constellation Lyra. Scientists intrigued by 2014 data from the Kepler Space Telescope decided to revisit the two planets using the Hubble Space Telescope and NASA's retired Spitzer Space Telescope in hopes of better understanding the distant worlds and what they're made of. And surprisingly, the answer might be mostly water.

"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," Björn Benneke, a planetary astrophysicist at the Université de Montréal in Canada and a co-author on the new research, said in a statement.

"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," he said. "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."

More:
https://www.space.com/exoplanets-potential-water-worlds-discovered