Exoplanet Found with All 3 Life Conditions for First Time
For the first time, astronomers have detected an atmosphere on a rocky exoplanet orbiting within the habitable zone of its star — fulfilling all three essential conditions for life as we know it on a single world beyond our solar system. The landmark discovery, published in the journal Science on July 16, marks a major milestone in the decades-long search for extraterrestrial life.
The planet, designated LHS 1140b, is a super-Earth located approximately 48 light-years from Earth in the constellation Cetus. Using the Magellan Clay telescope at Las Campanas Observatory in Chile’s Atacama Desert, an international team led by Collin Cherubim of the Harvard-Smithsonian Center for Astrophysics detected helium escaping from the planet’s upper atmosphere via transit spectroscopy — confirming the presence of an atmosphere for the first time on a rocky world in the habitable zone.
The Three Conditions
As explained by Prof. Katrien Kolenberg, a Belgian astrophysicist at the University of Antwerp and KU Leuven, the three necessary conditions for life as we know it are a rocky surface, a location in the habitable zone where liquid water can exist, and an atmosphere to regulate climate and shield against radiation. While LHS 1140b was already known to satisfy the first two, the detection of an atmosphere now completes the trifecta.
“This is truly a milestone,” Kolenberg told VRT NWS. “Atmospheres had been detected around gas planets, without a solid surface, or around planets outside the habitable zone of their star, but here we have for the first time strong indications of an atmosphere around a rocky planet in the habitable zone of its star.”
What Astronomers Found
LHS 1140b is about 5.6 times as massive as Earth and 1.73 times Earth’s radius — dimensions consistent with a rocky composition shrouded in a gaseous atmosphere or a global ocean. It orbits the red dwarf star LHS 1140 every 24.7 days at a distance of 0.0957 AU. Because its host star is a dim red dwarf, the planet receives less than half the sunlight Earth gets, placing it squarely in the habitable zone.
The researchers observed LHS 1140b as it transited — passed in front of — its star. By analyzing the starlight filtering through the planet’s upper atmosphere, they detected the distinct spectral fingerprint of helium. The helium signal appeared both before and after the transit, forming leading and trailing tails, indicating that approximately 100,000 kilograms of helium are escaping per second.
“Really, the most exciting thing here is that the planet has an atmosphere at all,” Cherubim told Science News. “It’s been a major goal in the field of exoplanets to find atmospheres on rocky exoplanets.”
The system also contains LHS 1140c, a closer-in planet that completes an orbit in under four days and shows no discernible atmosphere. This contrast establishes what astronomers call the “cosmic shoreline” — the boundary between airless rocks and planets with stable atmospheres — within a single star system.
A Surprising Atmosphere
The discovery carries particular significance because red dwarf stars, the most common type in the galaxy, are known for producing harsh radiation and stellar flares that can strip planetary atmospheres. The fact that LHS 1140b has retained its atmosphere for at least 3 billion years — and could maintain it for another billion — demonstrates that rocky planets can preserve atmospheres even in challenging environments.
Laura Kreidberg of the Max Planck Institute for Astronomy in Heidelberg told Nature that the finding makes her “more optimistic now about the chances of habitable environments beyond the solar system.” She described LHS 1140b as “a kind of planet that we’ve never seen before” — too thick an atmosphere for a bare rock, but not thick enough to be a gas giant.
Sara Seager, an astrophysicist at MIT, called the findings an “amazing missing piece of the puzzle” regarding whether rocky exoplanets can have atmospheres, as reported by Nature.
Caveats and Next Steps
Despite the excitement, researchers are careful to note important caveats. The detection is limited to helium in the upper atmosphere — the composition of the lower atmosphere remains unknown. Whether water vapor, carbon dioxide, nitrogen, or methane exist closer to the surface is a question for future observations.
“The only certainty we have for now is that there is life on Earth,” Kolenberg cautioned in her interview with VRT NWS. These conditions are necessary for life, she emphasized, but not sufficient.
Follow-up observations with the James Webb Space Telescope (JWST) are expected to determine the full atmospheric composition. The Extremely Large Telescope (ELT), currently under construction in Chile’s Atacama Desert with Belgian participation, is expected to revolutionize exoplanet studies when it becomes operational around 2030.
What This Means for the Search for Life
The discovery validates a key strategy in the search for extraterrestrial life: searching for atmospheres on rocky planets in habitable zones. By demonstrating that all three necessary conditions can coexist, the finding dramatically expands the number of potentially habitable worlds in the galaxy.
As BBC News reported, lead author Cherubim described the discovery as “a big deal,” noting that “this is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star.”
The research, published in Science, opens a new chapter in astrobiology. While LHS 1140b itself may not harbor life — its tidally locked rotation means one side faces perpetual daylight and the other eternal darkness — its existence proves that the conditions necessary for life can and do assemble on worlds beyond our own. The question of whether any of those worlds actually host life remains the greatest open question in science.