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Astronomers at MIT, Harvard University, and elsewhere have searched a rocky, Earth-sized exoplanet for signs of an atmosphere — and found none.
Atmospheres have previously been detected on planets much larger than our own, including several hot-Jupiters and sub-Neptunes, all of which are primarily made of ice and gas. But this is the first time scientists have been able to nail down whether an Earth-sized, terrestrial planet outside our solar system has an atmosphere.
The planet in question, LHS 3844b, was discovered in 2018 by NASA’s Transiting Exoplanet Survey Satellite, TESS, and was measured to be about 1.3 times larger than Earth. The planet zips around its star in just 11 hours, making it one of the fastest orbiting exoplanets known. The star itself is a small, cool M-dwarf that resides just 49 light-years from Earth.
In a paper published today in Nature, the team reports that LHS 3844b likely has neither a thick, Venus-like atmosphere nor a thin, Earth-like atmosphere. Instead, the planet is probably more similar to Mercury — a blistering, bare rock. If an atmosphere ever existed, the researchers say the star’s radiation likely blasted it away early in the planet’s formation.
“We basically found a hot planet with no gases around it,” says co-author Daniel Koll, a postdoc in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “This is the first time we’ve known anything in detail about the atmosphere of a planet around these M-dwarfs, which are the most common type of star, making LHS 3844b the most common type of rocky planet in the galaxy.”
Could any form of life manage to take hold in such a barren wasteland? Koll and his colleagues say it’s extremely unlikely, as the lack of an atmosphere would instantly cook off any organisms on the planet’s surface. But that doesn’t mean other terrestrial exoplanets are similarly without cover.
“We never thought this particular planet would be hospitable for life,” says lead author Laura Kreidberg, a researcher at the Harvard Center for Astrophysics. “It’s more a question of whether this whole category of planets around smaller stars has atmospheres or not. And our technique is a robust way of assessing whether an atmosphere is present or not.”
Kreidberg and Koll’s co-authors from MIT include Jason Dittmann, Ian Crossfield, David Berardo, Xueying “Sherry” Guo, George Ricker, Sara Seager, and Roland Vanderspek, along with colleagues from Harvard, the University of Texas at Austin, the Jet Propulsion Laboratory, Caltech, Stanford University, the University of Maryland, and Vanderbilt University.
Faces exposed
In 2018, LHS 3844b was among the first crop of extrasolar worlds confirmed by TESS, an MIT-developed satellite that monitors thousands of the closest, brightest stars, for transits — periodic dips in starlight that could signal a planet orbiting in front of the star, momentarily blocking its light.
Kreidberg and her team flagged LHS 3844b as an ideal laboratory, as its star is bright and nearby, and therefore a source against which scientists could study the planet in detail. As LHS 3844b is extremely close to its star, and thus incredibly hot, Kreidberg and Koll reasoned that it should give off enough heat to reveal clues as to whether it hosts an atmosphere.
Source
http://news.mit.edu/2019/earth-exoplanet-no-atmosphere-0819