Astronomers Detect Atmosphere on Rocky Exoplanet LHS 1140 b in Habitable Zone

For the first time, astronomers have confirmed an atmosphere on a rocky exoplanet in the habitable zone, LHS 1140 b, located 49 light-years from Earth. The discovery, published in Science on July 16, was led by Collin Cherubim (Harvard, now University of Chicago) and Shreyas Vissapragada (Carnegie Observatories). Using the WINERED instrument on the Magellan Clay Telescope in Chile, the team detected excited helium atoms in the planet's upper atmosphere in 2024, though follow-up observations in 2025 showed no escaping helium, suggesting the phenomenon is intermittent. LHS 1140 b, discovered in 2017, is a super-Earth with 1.7 times Earth's radius and 5.6 times its mass, orbiting a red dwarf star every 25 days. The atmosphere likely contains abundant helium and little hydrogen, with water possibly in the lower atmosphere. No evidence of life exists, but the planet has essential ingredients for habitability. A second rocky exoplanet in the system, LHS 1140 c, showed no atmosphere, illustrating the 'cosmic shoreline' concept where some worlds retain atmospheres while others lose them. External experts Sara Seager (MIT) and Charles Cadieux (University of Montreal) praised the detection but urged caution due to inconsistent helium signals.