Exoplanet evolution? Mini-Neptunes may shed their atmospheres and become super-Earths

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New research suggests that stellar radiation may commonly strip away the atmospheric outer layers of exoplanets slightly smaller than Neptune, transforming them into super-Earths.

Exoplanet evolution? Mini-Neptunes may shed their atmospheres and become super-Earths : Read more

 

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The article reports about the two exoplanets, "The researchers used the Hubble Space Telescope and the W.M. Keck Observatory in Hawaii to observe four mini-Neptunes. They noticed that two of their subjects — one called HD 63433c located 73 light-years away from Earth, and another called TOI 560.01 found 103 light-years away — had fast-moving gas in their atmospheres. "The speed of the gases provides the evidence that the atmospheres are escaping," said Zhang. "The observed helium around TOI 560.01 is moving as fast as 20 kilometers [12.4 miles] per second, while the hydrogen around HD 63433c is moving as fast as 50 kilometers [31.1 miles] per second."

Properties for HD 63433 c can be seen at this site, The Extrasolar Planet Encyclopaedia — HD 63433 c (exoplanet.eu)

Currently the site shows 1620 exoplanets with radii 1.7 to 3.9 earth radii size. There are other reports of exoplanets losing their atmospheres like various hot jupiters too. Such exoplanet systems are very different than our solar system.

Reference paper, Detection of Ongoing Mass Loss from HD 63433c, a Young Mini-Neptune, https://iopscience.iop.org/article/10.3847/1538-3881/ac3f3b, 17-Jan-2022. "Abstract We detect Lyα absorption from the escaping atmosphere of HD 63433c, a R = 2.67R⊕, P = 20.5 day mini-Neptune orbiting a young (440 Myr) solar analog in the Ursa Major Moving Group..."