Scientists Discover LHS 1140b, the Most Earth-like Exoplanet Yet
Summary
jeffrey-kluger (Time) reports on a Science study led by collin-cherubim (university-of-chicago) confirming that lhs-1140b, a rocky exoplanet ~48 light-years away orbiting the quiet M dwarf lhs-1140, is the first known exoplanet to combine the right size, a habitable-zone orbit, and a confirmed atmosphere. First discovered in 2017 via the transit method, the planet’s mass was later refined via radial-velocity. Cherubim’s team predicted and then confirmed an atmosphere by detecting helium bleed-off during transit spectroscopy; climate models suggest CO₂, CO, trace O₂, and abundant water may lie beneath the helium. The host star’s unusually low X-ray output (~10x Earth’s, versus Proxima Centauri’s ~400x) makes LHS 1140b substantially more favorable to surface life than other nearby habitable-zone candidates like gj-887-d.
Key Claims
- LHS 1140b is the first exoplanet confirmed to have the right size, habitable-zone temperature, and a confirmed atmosphere simultaneously — “at the forefront for studying astrobiology and habitability” (Cherubim).
- Discovered in 2017 via the transit method; orbits lhs-1140 every 24.7 days at ~9 million miles, versus Earth’s 93M-mile solar distance.
- Diameter ~1.7x Earth’s; mass ~5.6x Earth’s (via radial-velocity).
- Atmosphere confirmed by detecting helium absorption in the planet’s transit spectrum, following a predictive climate model Cherubim built during his Harvard PhD.
- Cherubim’s models predict CO₂ as the second most abundant atmospheric gas, plus CO, trace molecular O₂, and substantial water.
- lhs-1140’s X-ray flux (~10x Earth’s) is far below Proxima Centauri’s (~400x Earth’s, which has likely sterilized Proxima Centauri b), reducing atmosphere-stripping/life-preventing radiation risk.
- The study does not claim evidence of actual life on LHS 1140b.
Notable Quotes
“[A living world] has got to be the right temperature to sustain liquid water on the surface, and it has to have an atmosphere to hold that water in place and to shield the surface from ionizing radiation. LHS 1140b has all three of these things. That puts it at the forefront for studying astrobiology and habitability and looking for life outside the solar system.” — Collin Cherubim
“My models do predict carbon dioxide to be the second most abundant gas, and carbon monoxide to be present, and also small amounts of O2 molecular oxygen. From our climate modeling, we’ve also predicted a lot of water on this planet.” — Collin Cherubim
“Right now on LHS 1140B, the amount of X-ray flux would not really be threatening to life as we know it at all.” — Collin Cherubim