First Atmosphere Confirmed on Rocky Habitable-Zone Exoplanet
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- LHS 1140b — a rocky exoplanet 49 light-years away with mass 5.6× Earth's and radius 70% larger — has been confirmed to have an atmosphere, the first such detection on a rocky planet in its star's habitable zone
- Dr Collin Cherubim and colleagues detected escaping helium using the Magellan Clay telescope at Las Campanas Observatory in Chile, publishing in the journal Science
- The 2024 data revealed helium escaping into space; the team ruled out Earth-atmosphere contamination, but helium was not detected in 2025 follow-up observations, which Cherubim called "a shock"
- LHS 1140b orbits a quiet red dwarf in the constellation Cetus, is tidally locked, and could harbor far more water than Earth; no atmosphere was found on sibling planet LHS 1140c
- Professor Jayne Birkby of Oxford called the finding "a crucial step" toward understanding habitability around red dwarf stars, noting the atmosphere's signal varies with extreme UV radiation from the host star
- Dr Yamila Miguel of Leiden Observatory cautioned the helium signal reflects gas escaping from the upper atmosphere, not the lower atmosphere where life would evolve — "no direct implications for detecting life on other planets"
Why it matters: This is the first confirmed atmosphere on a rocky habitable-zone exoplanet, a milestone because LHS 1140b now checks all three habitability boxes: rocky composition, liquid-water temperatures, and a protective envelope. But Miguel's caveat matters — the detected helium is escaping from the upper atmosphere, not the surface layer where life would actually evolve, so this is a habitability candidate, not yet a biosignature.
