An international group of astronomers obtained the most intricate map of a rocky super-earth exoplanet, revealing that it has halves: one side is almost completely solid, while the other side has molten lava.

Exoplanet 55 Cancri e, which is nearly twice as big as Earth, possesses the most extreme temperature swings that may have caused its atmosphere to evaporate, resulting to the "two-faced" conditions on the planet.

Temperatures on the "toasty" side of the exoplanet can reach 4,400 degrees Fahrenheit. In contrast, the "cool" side of the exoplanet is about 2,060 degrees Fahrenheit, researchers said.

"Our view of this planet keeps evolving," said report lead author Brice Olivier Demory.

He and his colleagues used data from NASA's Spitzer Space Telescope to examine 55 Cancri e, which revolves around a host star located 40 light years away in the Cancer constellation.

The team mapped out how conditions on the exoplanet shift throughout a complete orbit - the first feat for such a small planet.

55 Cancri e is tidally "locked", meaning that the same phase always faces its host star.

This is very similar to the phases of our moon. When compared to Earth, where the atmosphere helps circulate heat, 55 Cancri e has a molten day side and a completely solid night side.

Demory, who is an astrophysicist from the University of Cambridge, said this means that the planet does not efficiently transport heat. He said this could be explained by the lack of atmosphere on the day side, or by lava flows at the surface of the planet.

Michael Gillon, Demory's colleague, said the day side of the exoplanet could possibly contain rivers of lava, as well as big pools of hot magma. The night side could possibly have solidified lava flows, similar to the ones in Hawaii, he said.

Meanwhile, Demory said they have yet to find other small planets that orbits this close to its parent star while at the same time being relatively close to Earth. He said 55 Cancri e offers a lot of possibilities for detailed observations on the atmospheric and surface conditions of rocky exoplanets.

One question they would want to answer is this: where exactly does the additional heat on 55 Cancri e come from in the first place?

Observations reveal an unknown source of heat that makes the exoplanet hotter than expected just from the star's irradiation, but researchers may have to wait for the next generation of space telescopes to find out the answer.

In the meantime, the scientists plan to keep studying the molten exoplanet to uncover more secrets it might hold. Their current findings are published in the journal Nature.

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