The discovery of an atmosphere clinging to a rocky planet capable of holding liquid water marks another quiet advance in our grasp of worlds beyond our own. Astronomers have detected helium escaping from the upper atmosphere of LHS 1140 b, a super-Earth roughly 5.6 times the mass of our planet.
This finding supplies the first observational evidence of an atmosphere on a rocky exoplanet situated in the habitable zone of its star. The planet orbits a cool red dwarf some 48 light years from Earth and was first identified in 2017. Its radius measures about 1.7 times that of Earth.
Observations came from the Magellan Clay Telescope in Chile, timed to the planet's transits in 2024 and 2025. Helium showed up clearly during the 2024 transit yet remained absent in the 2025 follow-up, a pattern that points to variable rates of atmospheric escape.
The study, published in the journal Science this month, rests on careful transit spectroscopy. As the planet passed in front of its star, excess absorption in the data aligned with helium streaming away from the upper atmosphere. Such signals had long been predicted by models yet required persistent monitoring to confirm.
First and foremost, helium just tells us that there is an atmosphere, period. It is a binary, yes-no thing.
Collin Cherubim, lead author of the study and then a doctoral student at Harvard University, offered that straightforward assessment. The binary nature of the detection matters because earlier claims of atmospheres around rocky habitable-zone worlds had rested on indirect or contested evidence. Here the signal is direct.
Cherubim put the result in sharper relief elsewhere: "This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star." The remark underscores how methodical refinement of instruments and repeated observations can turn theoretical possibility into measured fact.