Exoplanets are planets orbiting around other stars outside our solar system. Exoplanets comes in different shape, size. Astronomers using Hubble Space Telescope & W.M Keck Observatory have observed two Mini-Neptunes losing their atmospheres and becoming Super-Earths. The new findings were published in two separate papers in The Astrophysical Journal.
According to NASA, Mini-Neptunes are smaller and denser versions of the planet Neptune and consist of a rocky core blanketed with thick gas. Mini-Neptunes are between 2 and 4 times the size of Earth. Super-Earths are rocky and are large as 1.6 times the size of Earth.
In this study, a team of astronomers used NASA’s Hubble Space Telescope to study the HD 63433c which is a mini-Neptune orbiting HD 63433, a G-type star located 73 light years away. They used the W.M Keck Observatory in Hawaii to study the mini-Neptune TOI 560.01 which orbits TOI 560 & is located at 103 light years away. TOI 560.01 is about two times the size of Earth and has a puffy atmosphere, made up of mostly Hydrogen & Helium.
These two mini-Neptunes are losing their puffy atmosphere & likely transforming into super-Earths. Radiation from their host star is stripping away their atmospheres.
Using W.M. Keck observatory in Hawaii scientists revealed that Helium is escaping from the TOI 560-01. The observed helium around TOI 560-01 is moving as fast as 20kms/second, while the Hydrogen around HD 63433c is moving as fast as 50Kms/Second. The gravity of these mini-Neptunes is not strong enough to hold on to such fast moving gas. This means in several hundred years to millions of years, they will lose their atmospheres, leaving behind rocky cores.
The study also found that the gas around TOI 560.01 was escaping toward the star. “This was unexpected as most models predict that the gas should flow away from the star,” said Heather Knutson, professor of Planetary Science at Caltech & co-author of this study. This new discovery will help astronomers understand how these worlds evolve.