Astronomers have detected an atmosphere surrounding LHS 1140b, a rocky exoplanet located 48 light-years away in the habitable zone of its host star. Published in the journal Science, the discovery marks the first time researchers have confirmed an atmosphere on a rocky planet in the habitable zone of another star.
The search for life beyond Earth has long been hindered by the difficulty of confirming whether small, rocky planets can retain a gaseous envelope. Many astronomers feared that red dwarf stars, which are the most common stars in the galaxy, emitted enough high-energy radiation to strip such atmospheres away early in a planet’s life. The findings regarding LHS 1140b, however, suggest that some rocky worlds can indeed hold onto an atmosphere for billions of years.
Evidence of a Helium-Rich Atmosphere
The study, led by researchers affiliated with Harvard University, utilized data captured by the Magellan Clay telescope at Las Campanas Observatory in Chile. By observing the planet as it transited its host star, the team identified the presence of helium. While helium alone is not typically associated with life-sustaining conditions, its presence is a critical first step in atmospheric characterization.
“This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star.”
Dr. Collin Cherubim, lead author and Harvard PhD graduate
The researchers believe the atmosphere may be highly layered. While the upper regions are dominated by helium and depleted of hydrogen, the team predicts that other chemical species, such as water vapor, carbon dioxide, or oxygen, could be trapped at lower altitudes closer to the surface. This hypothesis remains to be confirmed by future observations, as current data primarily reveal the composition of the outer, escaping gas.
The Challenges of Red Dwarf Systems
LHS 1140b orbits an M-class dwarf star, a type of star known for being significantly more active than our sun. These stars frequently produce solar flares and coronal mass ejections (CMEs) that can erode planetary atmospheres. The detection of an atmosphere on LHS 1140b serves as a landmark, proving that such environments are not universally destroyed by their host star’s activity.
However, the atmospheric state appears to be dynamic. Observations from 2024 showed helium escaping from the planet, whereas follow-up data from 2025 did not show the same signal.
Comparing Candidates in the Search for Life
The scientific community has been monitoring several other high-profile candidates, including the TRAPPIST-1 system and K2-18b.
LHS 1140b distinguishes itself through its composition. Unlike sub-Neptunes or gas giants, LHS 1140b is a confirmed rocky world with a mass roughly 5.6 times that of Earth. As noted by CNET, the planet meets the three primary criteria for habitability: it is rocky, sits in the Goldilocks zone
where temperatures allow for liquid water, and possesses an atmosphere. Whether that atmosphere contains gases conducive to life, however, is a question for future missions.
Next Steps for Atmospheric Characterization
The focus for the scientific community now shifts to confirming the stability of the atmosphere and searching for heavier molecules. Astronomers expect that data from the JWST will be instrumental in determining if the planet holds a persistent, life-supporting atmosphere or if it is merely a bare rock that occasionally vents gas.
While researchers prepare for these detailed observations, the discovery has already reshaped expectations for what can be found around M-dwarf stars. The ability to detect an atmosphere on a planet 48 light-years away demonstrates that the current generation of instrumentation is reaching the resolution limits necessary to study the chemical makeup of potentially habitable worlds, setting the stage for more advanced studies in the coming decade.
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