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New map of rocky ‘Super Earth’ unveils lava world

Thursday, Mar 31, 2016,13:08 IST By Metrovaartha A A A

Washington | Scientists, including one of Indian-origin, have obtained the most detailed map of a super-Earth planet for the first time, that consists of two halves – one that is almost completely molten and the other mostly solid. Using data from NASA’s Spitzer Space Telescope, researchers found that temperatures on the hot side can reach 2,500 degrees Celsius, while temperatures on the cool side are around 1,100 degrees Celsius.

The latest findings tell us the planet has hot nights and significantly hotter days. This indicates the planet inefficiently transports heat around the planet, said study lead author Brice Olivier Demory of the University of Cambridge in the UK. We propose this could be explained by an atmosphere that would exist only on the day side of the planet, or by lava flows at the planet surface, said Demory.

The toasty super-Earth 55 Cancri e is relatively close to Earth at 40 light-years away. It orbits very close to its star, whipping around it every 18 hours. Due to its proximity to the star, it is tidally locked by gravity just as Moon is to Earth. That means one side of 55 Cancri, referred to as the day side, is always cooking under the intense heat of its star, while the night side remains in the dark and is much cooler.

Spitzer observed the phases of 55 Cancri e, similar to the phases of the Moon as seen from the Earth. We were able to observe the first, last quarters, new and full phases of this small exoplanet, said Demory. The Spitzer telescope watched the planet for a total of 80 hours, as it was orbiting around its star multiple times. The data allowed scientists to map temperature changes across the planet.

The fact Spitzer found the night side to be significantly colder than the day side means heat is not being distributed around the planet very well. The findings suggest a planet devoid of a massive atmosphere, and possibly hint at a lava world where the lava would become hardened on the night side and unable to transport heat.

The day side could possibly have rivers of lava and big pools of extremely hot magma, but we think the night side would have solidified lava flows like those found in Hawaii, said Michael Gillon, from University of Liege in Belgium.

The Spitzer data also showed the hottest spot on the planet has shifted over a bit from where it was expected to be – directly under the blazing star. This shift either indicates some degree of heat recirculation confined to the day side, or points to surface features with extremely high temperatures, such as lava flows.

We have entered a new era of atmospheric remote sensing of rocky exoplanets, said Nikku Madhusudhan, from the Institute of Astronomy at Cambridge. It is incredible that we are now able to measure the large scale temperature distribution on the surface of a rocky exoplanet, Madhusudhan said.

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