Astronomers discover strange twin planets might be water worlds

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.

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