(ORDO NEWS) — An international team of astronomers has discovered two young mini-Neptune exoplanets with an actively evaporating atmosphere. It is assumed that as a result of this process, rocky terrestrial planets can form.
Mini-Neptunes, or gas dwarfs, are a class of exoplanets that resemble the structure of Neptune in our solar system, but are inferior to it in mass. Such planets have a solid rocky core and a thick gaseous shell, mainly consisting of hydrogen and helium.
In two recent studies ( 1 , 2 ), published in the same issue of The Astronomical Journal , an international team of scientists report the discovery of two young mini-Neptunes losing their atmosphere to their parent stars.
The process of evaporation of the atmosphere of gaseous dwarfs was able to be fixed, based on data from the Hawaiian Keck Observatory ( WM Keck Observatory ) and the Hubble Space Telescope .
“Most astronomers suspected that the atmosphere of young, small mini-Neptunes must be evaporating,” says Michael Zhang , lead author of both studies and a graduate student at the California Institute of Technology. “But so far, no one has ever been able to capture the evaporation process itself.”
Direct observation of the evaporation of the atmospheres of gas dwarfs confirms one of the theories of the formation of super-Earths.
According to her, if the mini-Neptune is small enough and is close enough to the parent star, its X-ray and ultraviolet radiation can deprive the exoplanet of the primary atmosphere for hundreds of millions of years.
As a result of the evaporation process, a super-Earth remains in place of the gas dwarf – a rocky terrestrial planet with a much smaller radius. In theory, such a super-Earth could retain the remnants of an atmosphere similar to that of our Earth.
In addition to the very fact of evaporation, astronomers noticed one interesting feature: the gas from the atmosphere of the mini-Neptune TOI 560.01, which makes a revolution around the parent orange dwarf in just 6.4 days, leaves mainly towards the star.
Future observations of other mini-Neptunes should show whether the case of TOI 560.01 can be called the rule or rather an anomaly.
“This was unexpected, since most models predict that the gas should flow away from the star,” said Heather Knutson, professor of planetary science at Caltech, Heather Knutson , Zhang’s consultant and co-author of the study. “We still have a lot to learn about what is really happening with these gas flows.”
The HD 63433 system, consisting of a yellow dwarf and two mini-neptunes, HD 63433b and HD 63433c, also had its own features.
The paper clearly shows that the atmosphere of HD 63433c with a radius of 2.67 times that of the Earth is actively evaporating. At the same time, the second mini-Neptune HD 63433b (smaller than the first and closer to the parent star) has probably already lost its primary atmosphere.
Contact us: [email protected]