Changes in super-Earth atmosphere observed for first time

High volcanic activity might be behind wild temperature variation

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55 Cancri e is so close to its host star that its year lasts only 18 Earth days.
Credit: Uni. Texas, NSF, NASA

By Elizabeth Pearson

Atmospheric changes have been detected on a super-Earth for the first time. Researchers measured a near threefold change in the temperature of exoplanet 55 Cancri e over a two year period. While the cause of this change is still uncertain, it’s believed that extreme volcanism might be present on the planet’s surface.

The team behind the discovery have been studying 55 Cancri e with NASA’s Spitzer Space Telescope for several years. The planet is a super-Earth, a rocky planet two to ten times the mass of our planet, orbiting around a Sun like star 40 light years away in the constellation of Cancer. 

The planet is tidally locked, meaning that the ‘day side’ is always facing towards the star. However, over the course of two years of observations the temperature of the day side swung between 1000 and 2,700°C.

“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,” said Dr. Nikku Madhusudhan of Cambridge’s Institute of Astronomy. “No signature of thermal emissions or surface activity has ever been detected for any other super-Earth to date.”

The variations in temperature could be caused by huge plumes of gas and dust periodically blanketing the surface, perhaps caused by exceptional levels of volcanic activity. If volcanism was the culprit then the activity on 55 Cancri e would have to be far greater than what has been observed even on Jupiter’s moon Io, the most volcanic body in our Solar System.

“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 – clues can come from unexpected quarters,” says Madhusudhan.

Though changes have been observed in planetary atmospheres before, these results are unique because they come from a rocky world. All previous measurements had been from gas giants which, due to their larger size, are considerably easier to observe. This new observation has shown that it is possible to take these readings of smaller planets as well.

“The present observations open a new chapter in our ability to study the conditions on rocky exoplanets using current and upcoming large telescopes,” says Madhusudhan.


 

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