Astronomers spot two 'puffy' mini-Neptune exoplanets that are losing their atmospheres 'like steam from a pot of boiling water' and transforming into super-Earths
Two 'mini-Neptune' exoplanets that are losing their atmospheres 'like steam from a pot of boiling water' have been discovered by astronomers.
Experts say the worlds are likely transforming into 'super-Earths' because radiation from nearby stars is stripping away their 'puffy' atmospheres and driving hot gas to escape.So-called mini-Neptunes, which have large, rocky cores surrounded by thick blankets of gas, are smaller, denser versions of the eighth planet from the sun in our solar system.
They are one of two types of commonly seen exoplanets that fall into the category of being smaller, rocky worlds which orbit close to their stars.
Two 'mini-Neptune' exoplanets that are losing their atmospheres 'like steam from a pot of boiling water' have been discovered by astronomers. One is pictured in this artist's impression
Neither type of planet is found in our solar system.
The mini-Neptune worlds revealed in the latest study, which was led by the California Institute of Technology (Caltech), are in star systems that are 103 and 73 light-years away, respectively.
Astronomers used the the W. M. Keck Observatory atop Maunakea in Hawaii to study two mini-Neptunes in the star system TOI 560, and the iconic Hubble Space Telescope to look at another pair orbiting HD 63433.
Their findings suggest that atmospheric gas is escaping from the innermost mini-Neptune in TOI 560, called TOI 560.01, and from the outermost mini-Neptune in HD 63433, called HD 63433 c.
The researchers believe this could mean that both are turning into super-Earths.
'Most astronomers suspected that young, small mini-Neptunes must have evaporating atmospheres,' said Michael Zhang, lead author of both studies and a graduate student at Caltech.
'But nobody had ever caught one in the process of doing so until now.'
Surprisingly, the researchers said, they also found the gas around TOI 560.01 was escaping predominantly toward its nearby star.
'This was unexpected, as most models predict that the gas should flow away from the star,' said Professor Heather Knutson, a co-author of the study.
'We still have a lot to learn about how these outflows work in practice.'
Since the first exoplanets orbiting sun-like stars were discovered in the mid-1990s, thousands of others have been found.
However, of those which are smaller, rocky worlds that orbit close to their star, few planets with sizes between super-Earths and mini-Neptunes have been detected.One possible explanation for this gap is that mini-Neptunes are transforming into super-Earth, the researchers said.
Mini-Neptunes are thought to be cocooned by primordial atmospheres made of hydrogen and helium.
The hydrogen and helium are left over from the formation of the central star, which is born out of clouds of gas.
If a mini-Neptune is small enough and close enough to its star, scientists think that stellar X-rays and ultraviolet radiation might strip away its primordial atmosphere over a period of hundreds of millions of years. One possible explanation for this gap is that mini-Neptunes are transforming into super-Earth, the researchers said.
Mini-Neptunes are thought to be cocooned by primordial atmospheres made of hydrogen and helium.
The hydrogen and helium are left over from the formation of the central star, which is born out of clouds of gas.
If a mini-Neptune is small enough and close enough to its star, scientists think that stellar X-rays and ultraviolet radiation might strip away its primordial atmosphere over a period of hundreds of millions of years.
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