Super-Earth sports hot zone warm enough to melt iron
NASA/JPL-Caltech

Super-Earth sports hot zone warm enough to melt iron

Most of the little we know about conditions on alien worlds comes from gas giants like Jupiter, simply because they’re big and easier to detect. But researchers are zooming in on smaller bodies, and today they reveal a basic temperature map of 55 Cancri e (imagined by an artist, above), a super-Earth around a sunlike star just 40 light-years away—the first time features have been discerned on such a small planet. The world may have a diameter just twice that of ours and weigh about nine times as much, but conditions there aren’t remotely Earth-like. It’s so close to its parent star that its “year” is a mere 18 hours long and temperatures are scorchingly hot. Observations with the Hubble Space Telescope last year revealed the planet has an atmosphere of hydrogen, helium, and a touch of hydrogen cyanide. Now, a team using the Spitzer Space Telescope, which observes in the infrared, reports in Nature today that the planet has huge variations in temperature across its surface. 55 Cancri e is tidally locked with its star, so the same face of the planet is always illuminated. The middle of the star-facing side isn’t its hottest point, however; that lies 41° to the east. The hot spot has a temperature of 2400°C—hot enough to melt iron—whereas the dark face is 1300°C cooler. The dramatic temperature change suggests, the researchers say, a thick atmosphere with circulation restricted to the dayside, or no atmosphere at all so heat can only shift via slow-moving magma. Either way, it’s a planet where going over to the dark side could be blessed relief.