A rocky super-Earth 48 light-years away, approximately 1.7 times the diameter and 5.6 times the mass of our planet, may be capable of sustaining life. The exoplanet, LHS 1140 b, was leaking helium, which could be indicative of the presence of an atmosphere, a necessary factor for life to flourish.
A whole new world
LHS 1140 b likely has an “upper atmosphere dominated by helium and depleted in hydrogen, with other volatile species trapped at lower altitudes,” said a study published in the journal Science. The exoplanet was discovered in 2017 and was found to share many qualities with Earth. Though its temperatures are colder than our planet’s, it “orbits a red dwarf star within the star’s habitable zone,” which is the sweet spot “where temperatures and environmental conditions are within the range that could support liquid water on the planet’s surface,” said a news release about the study. This is the “first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star,” Collin Cherubim, the lead author of the study, said in the release.
The researchers were able to identify the exoplanet’s atmosphere using a technique that is “typically reserved for observing giant planets,” and using it “for a rocky planet, which nobody has done before,” Cherubim said to Space.com (a sister site of The Week). With the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan Observatory in Chile, they were “able to see LHS 1140 b and another planet both transit, or pass in front of, their star in the same night,” where they could “identify the signatures of molecules in the atmospheres of these planets as they passed,” said Space.com. One planet “yielded no results,” but LHS 1140 b “showed a direct, undeniable helium signature.”
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Helium is a “very light gas that easily escapes gravity,” so it “could serve as a readily detectable marker of a complex atmosphere underneath,” said Time. A potential atmosphere is a significant find as small red dwarf planets are the “most common type of star, and hence our best chance for studying nearby rocky exoplanets in their habitable zone,” said The Guardian. Red dwarfs aren’t as bright as our sun, so their planetary habitable zone tends to be in the range of solar flares, which often strip “away the atmospheres from the planets they host, leaving rocky planets with thin atmospheres or airless.”
Endless diamond sky
While the findings are promising, “at this point, we have absolutely no evidence for life on the planet,” Cherubim said to The New York Times. “But we think all of the really important, essential ingredients are there.” The question remains whether LHS 1140 b is “bare rock with no atmosphere that sometimes burps up some gas that then immediately escapes,” or if there is a “steady-state atmosphere there that will leak out stuff like the Earth does from time to time,” Jason Dittmann, an assistant professor of astronomy at the University of Florida and the one who first found the planet, said to The Independent.
An atmosphere helps a planet hold water, regulate climate and protect from space radiation. To determine whether the helium leak is from an atmosphere, NASA’s James Webb Space Telescope will be used to “look for water, and if there’s water in the atmosphere, then it’s probably a stable atmosphere that will persist,” said Dittman to The Independent. Even if this exoplanet is not the next Earth, “if one potentially organic world is out there, countless others could be too,” said Time. The existence of potentially viable planets “dramatically” boosts the odds of alien life.
