LHS 1140 b Planet Found with Helium‑Rich Atmosphere in Habitable Zone

Astronomers have confirmed the first detection of an atmosphere around a rocky exoplanet located in its star’s habitable zone. Using near‑infrared transit spectroscopy with the WINERED spectrograph on the Magellan Clay telescope in Chile, they observed escaping helium from LHS 1140 b – a super‑Earth about 48–49 light‑years from Earth orbiting a quiet red‑dwarf star. The planet is roughly 1.7 × Earth’s radius and 5.6 × its mass, receiving about 42 % of Earth’s stellar irradiation, which places its surface temperature in a range that could allow liquid water.

Helium absorption was detected as the planet passed in front of its star in 2024, indicating a thin upper atmosphere losing gas to space. A simultaneous observation of the neighboring planet LHS 1140 c showed no helium signal, underscoring that LHS 1140 b retains a gaseous envelope while its companion does not. The helium outflow appears variable, with the signal absent in 2025 observations, suggesting changes in atmospheric escape rates.

The discovery, published in Science on 16 July 2026, provides the first direct evidence of an atmospheric species on a rocky world in a habitable zone and validates a new technique for probing exoplanet atmospheres. Researchers estimate the atmosphere may have persisted for billions of years, making LHS 1140 b a prime target for future studies of habitability and atmospheric composition with next‑generation telescopes such as JWST.