Temperature Swings Thousands of Degrees on Hellish Super Earth

Artist’s impression of super-Earth 55 Cancri e, showing a hot partially-molten surface of the planet before and after possible volcanic activity on the day side / NASA/JPL-Caltech/R. Hurt
Janet Fang 06 May 2015, 19:05

Vast amounts of volcanic activity may be triggering wild, fiery fluctuations in temperature on a super-Earth called 55 Cancri e. These rapid changes include temperature swings of over a thousand degrees. The work, available online at arXiv, is the first time astronomers have observed variations in the atmosphere of a rocky planet outside of the solar system. 

55 Cancri e is twice the size of Earth, and eight times the mass. It orbits a sun-like star with four other exoplanets 40 light-years away in the constellation Cancer. It’s so close to its host star, a year lasts just 18 hours, and because the planet is tidally locked, it doesn’t rotate the way Earth does -- giving it a permanent “day” side and a “night” side.

Using NASA’s Spitzer Space Telescope, Cambridge’s Brice-Olivier Demory and colleagues observed a threefold change in temperature over the course of just two years. On the hot “day” side of the planet, the temperature swings between 1,000 and 2,700 degrees Celsius.

“This is the first time we’ve seen such drastic changes in light emitted from an exoplanet, which is particularly remarkable for a super Earth,” Cambridge’s Nikku Madhusudhan says in a news release. “No signature of thermal emissions or surface activity has ever been detected for any other super Earth to date.”

The causes of these turbulent temperature changes are still being investigated, though the team suspects they’re due to massive amounts of volcanic activity on the surface, which may be partially molten. “We saw a 300 percent change in the signal coming from this planet, which is the first time we’ve seen such a huge level of variability in an exoplanet,” Demory explains. “While we can’t be entirely sure, we think a likely explanation for this variability is large-scale surface activity, possibly volcanism, on the surface is spewing out massive volumes of gas and dust, which sometimes blanket the thermal emission from the planet so it is not seen from Earth.” (The rates of volcanic activity may even be higher than Jupiter’s Io.)

Previous observations of 55 Cancri e indicated a high abundance of carbon, suggesting that the planet was composed of diamond. “But now we’re finding that those measurements are changing in time. The planet could still be carbon rich, but now we’re not so sure -- earlier studies of this planet have even suggested that it could be a water world,” Madhusudhan adds. “The present variability is something we’ve never seen anywhere else, so there’s no robust conventional explanation. But that’s the fun in science.” 

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