First Atmosphere Detected on Rocky Exoplanet LHS 1140b
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- LHS 1140b has become the first rocky, temperate exoplanet with a confirmed atmospheric detection, located 50 light years from Earth and orbiting an M dwarf star.
- Collin Cherubim at Harvard University and colleagues identified the atmospheric signal in 2024 at Las Campanas Observatory in Chile, spotting excited helium atoms indicating an outflow leaking from a planetary atmosphere.
- The planet sits in its star's habitable zone, where temperatures could preserve liquid water on the surface.
- A follow-up 2025 observation with the same setup failed to detect the helium signature, and researchers don't yet understand why it appeared and then disappeared.
- LHS 1140b may fit the proposed category of "helium worlds," with potential surface pressures similar to the ocean floor, or possibly resembling an icy ocean moon more than any solar system world.
- Unpublished James Webb Space Telescope data could reveal the bulk atmosphere's size and composition, which researchers say is essential for assessing habitability.
Why it matters: Lead researcher Collin Cherubim called LHS 1140b "the best place to search for life outside of our solar system." The detection overturns earlier speculation that planets orbiting M-dwarf stars cannot retain atmospheres, opening a proposed "helium world" category. Unpublished JWST data could soon reveal whether surface conditions actually support liquid water.
