Björn Benneke

An artist’s rendering of the planet, called LP 791-18 d.Illustration: NASA’s Goddard Space Flight Center/Chris Smith (KRBwyle)On this world, the floor is lava and there’s no couch to jump to: Astronomers have described a planet that might be completely covered in active volcanoes. What Is Planet Nine and Why Can’t We Find It?Data from NASA’s Transiting Exoplanet Survey Satellite and the now deactivated Spitzer Space Telescope revealed an Earth-size rocky planet with some extreme features.The planet, called LP 791-18 d,…

An artist’s rendition of the Kepler-138 system, with the Earth-like water world Kepler-138d in the foreground.Illustration: NASA, ESA, L. Hustak (STScI)Astronomers using the Hubble Space Telescope have observed two exoplanets that may be examples of a long-hypothesized planetary classification: a water world.The planets are known as Kepler-138c and Kepler-138d and are located in a star system 218 light-years away, according to a release from the European Space Agency. The team, led by Caroline Piaulet of the Institute for…