The planet is probably tidally locked, meaning it perpetually has the same side facing its star, much like the moon does towards Earth. The planet is located in our Milky Way about 41 light-years from Earth, in the constellation Cancer. A light year is the distance light travels in a year, 9.5 trillion kilometres. Four other planets, all gas giants, are known to orbit its host star.

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That star is gravitationally bound to another star in a binary system. The other one is a red dwarf, the smallest kind of ordinary star. The distance between these companions is 1000 times the distance between Earth and the sun, and light takes six days to get from one to the other.

After all their searching, the rocky exoplanet for which scientists finally found evidence of an atmosphere turned out to be one that probably should not even have one. Being so close to its star, any atmosphere should be stripped away by stellar irradiation and winds. But gases dissolved in the vast lava ocean thought to cover the planet may keep bubbling up to replenish the atmosphere, Hu said.

“The planet cannot be habitable,” Hu said, because it is too hot to have liquid water, considered a prerequisite for life.

All the previous exoplanets found to have atmospheres were gaseous planets, not rocky ones. As Webb pushes the frontiers of exoplanet exploration, the discovery of a rocky one with an atmosphere represents progress.

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On Earth, the atmosphere warms the planet, contains the oxygen people breathe, protects against solar radiation and creates the pressure needed for liquid water to remain on the planet’s surface.

“On Earth, atmosphere is key for life,” Demory said. “This result on 55 Cnc [Cranci] e entertains the hope that Webb could conduct similar investigations on planets that are much cooler than 55 Cnc e, which could support liquid water at their surface. But we are not there yet.”

Reuters