Puffy Planets Lose Atmospheres Become Super-Earths, Known

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Play, download and edit the free video Puffy Planets Lose Atmospheres Become Super-Earths, Known As Mini-Neptunes TOI 560.01.

In this artistic animation that you seeing in the video shows, the mini-Neptune TOI 560.01 is shown transforming into a super-Earth. The planet is about 2.8 times the size of Earth and has a puffy atmosphere, made up of mostly hydrogen and helium. Observations with the W. M. Keck Observatory in Hawaii revealed that helium is escaping from the planet. Scientists say that the planet could lose the vast majority of its atmosphere after several hundred million years, leaving behind a type of large rocky planet called a super-Earth.

Now, astronomers have identified two different cases of "mini-Neptune" planets that are losing their puffy atmospheres and likely transforming into super-Earths. Radiation from the planets' stars is stripping away their atmospheres, driving the hot gas to escape like steam from a pot of boiling water. The new findings help paint a picture of how exotic worlds like these form and evolve, and help explain a curious gap in the size distribution of planets found around other stars.

Mini-Neptunes are smaller, denser versions of the planet Neptune in our solar system, and are thought to consist of large rocky cores surrounded by thick blankets of gas. In the new studies, a team of astronomers used NASA's Hubble Space Telescope to look at two mini-Neptunes orbiting HD 63433, a star located 73 light-years away. And they used the W. M. Keck Observatory in Hawaii to study one of two mini-Neptune planets in the star system called TOI 560, located 103 light-years away.

Their results show that atmospheric gas is escaping from the innermost mini-Neptune in TOI 560, called TOI 560.01 (also known as HD 73583b), and from the outermost mini-Neptune in HD 63433, called HD 63433 C. This suggests that they could be turning into super-Earths.

"Most astronomers suspected that young, mini-Neptunes must have evaporating atmospheres," said Michael Zhang, lead author of both studies and a graduate student at Caltech. The study also found, surprisingly, that the gas around TOI 560. 01 was escaping predominantly toward the star. "This was unexpected, as most models predict that the gas should flow away from the star," said professor of planetary science Heather Knutson of Caltech, Zhang`s advisor and a co-author of the study.

Many of these orbit close to their stars, and the smaller, rocky ones generally fall into two groups: the mini-Neptunes and super-Earths.

One possible explanation for this size-gap is that the mini-Neptunes are transforming into the super-Earths. The mini-Neptunes are theorized to be cocooned by primordial atmospheres made of hydrogen and helium. If a mini-Neptune is small enough and close enough to its star, stellar X-rays and ultraviolet radiation can strip away its primordial atmosphere over a period of hundreds of millions of years, scientists theorize. This would then leave behind a rocky super-Earth with a substantially smaller diameter (which could, in theory, still retain a relatively thin atmosphere similar to that surrounding our planet Earth).

"A planet in the size-gap would have enough atmosphere to puff up its radius, making it intercept more stellar radiation and thereby enabling fast mass loss," said Zhang. This latest discovery of two mini-Neptunes with escaping atmospheres represents the first direct evidence to support the theory that mini-Neptunes are indeed turning into super-Earths. The astronomers were able to detect the escaping atmospheres by watching the mini-Neptunes cross in front of, or transit, their host stars.

Credit: Space Sci Network

Editor: Azriel Robiso & Bellen Cañete
Lead Researcher: Azriel Robiso
Lead Producer: James Tralie
Lead Source and Writter: William Steigerwald
Lead Writter: Gage Taylor (KBR, Inc.)
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