Helium Escape Confirms First Atmosphere on Rocky Habitable-Zone Exoplanet LHS 1140b

For years, astronomers have hunted for atmospheres around rocky worlds in their stars’ habitable zones, and a team led by Harvard’s Dr Collin Cherubim has now secured the first confirmation. Using transit data collected in 2024 from the Magellan Clay telescope at Las Campanas Observatory in Chile, researchers detected helium escaping from LHS 1140b, a rocky super-Earth located about 48 light-years away the detection of helium escape that marks the first observationally confirmed atmosphere on any habitable-zone rocky exoplanet. The finding is significant because, while gas giants have shown atmospheric signatures for decades, proving even a tenuous envelope on a solid body requires measuring atoms literally drifting away from the planet.

The result was published in Science on July 16, 2026. Analysis of the transit data revealed a spectral signature consistent with helium escaping the planet’s upper atmosphere, validating the presence of an atmosphere that can be probed via escape detection rather than static absorption. This method allowed the team to characterize the outermost layers of the planetary envelope without needing to resolve LHS 1140b directly, overcoming the limitations imposed by its close orbit and the brightness of its host star.

The team also used the same dataset to examine the second planet in the system; data shows no atmosphere was detected around the companion planet LHS 1140c. Furthermore, follow-up observations conducted in 2025 failed to detect helium, indicating the atmospheric escape is time-variable. This fluctuation suggests the rate of loss can vary significantly over time, adding a dynamic constraint to models of how rocky worlds in habitable zones evolve under their host stars’ influence.

Researchers ruled out false positives in their analysis, ensuring the signal originates from planetary atmospheric loss rather than instrumental artifacts or stellar contamination. The confirmation of an atmosphere on LHS 1140b narrows the field of rocky habitable-zone candidates where atmospheres can be characterized; while other worlds have been studied, direct detection of helium escape here provides a definitive anchor for atmospheric mass-loss rates and demonstrates that volatile envelopes can persist on solid planets within regions where liquid water might exist.

This discovery shifts exoplanet atmospheric science from probabilistic inference to direct observation on habitable-zone rocky bodies. The helium envelope around LHS 1140b offers concrete data on how atmospheres can endure and how they are stripped over time, setting a foundation for future work that will determine whether heavier molecules survive alongside the lighter gases being lost to space.

Sources

• First atmosphere found around Earth-like planet LHS 1140b — BBC News
• Earth-like exoplanet found to have an atmosphere — The Guardian