LHS 1140 b Shows Signs of an Atmosphere Around a Nearby Red Dwarf

Astronomers have detected escaping helium from LHS 1140 b, a rocky super-Earth orbiting a red dwarf 48–50 light-years away in Cetus. The helium signal, observed during a 2024 transit, is interpreted as evidence that the planet retains a gaseous envelope—potentially the first confirmed atmosphere on a temperate rocky world outside the Solar System.

Scientists stunned: rocky planet’s atmosphere breakthrough could change everything for life Astronomy MagazineCNN

Since the first exoplanet discovery in the early 1990s, more than 6,300 planets have been catalogued, but none of the rocky planets in the habitable zones of M-dwarf stars had a confirmed atmosphere. M dwarfs are abundant and dim, making transits of small planets easier to detect, yet their frequent flares can strip atmospheres. LHS 1140 b, discovered in 2017, orbits a quiet red dwarf that emits far less visible light than the Sun, placing the planet in a region where surface temperatures could allow liquid water.

Astronomy MagazineScientists stunned: rocky planet’s atmosphere breakthrough could change everything for life CNN

• Mass: ~5.6 × Earth’s mass.

CNN

• Radius: Consistent with a rocky composition, suggesting an iron core, silicate mantle, and a low-density component (water and/or atmosphere).

CNN

• Orbit: 24.7-day period; receives ~42 % of Earth’s solar radiation.

Scientists stunned: rocky planet’s atmosphere breakthrough could change everything for life

• Helium Detection: Spectroscopic observations with the Magellan Clay Telescope in Chile recorded helium escaping from the upper atmosphere during a 2024 transit.

CNN

• Follow-up: A 2025 observation did not detect helium, indicating variability in atmospheric loss.

Scientists stunned: rocky planet’s atmosphere breakthrough could change everything for life

Lead author Collin Cherubim, a NASA Sagan Fellow at the University of Chicago, said the helium escape aligns with his model predicting early loss of hydrogen while helium can linger. He noted that helium alone is unlikely to support life, but its presence suggests heavier gases such as oxygen or water vapor could also be retained. Cherubim added that multiple facilities—including JWST and Hubble—plan to observe LHS 1140 b, and he has applied for additional time on a more sensitive instrument in Chile. Co-author Jason Dittmann described the discovery as “a sigh of relief” for the exoplanet community.

CNN

Michaël Gillon, research director of the Astrobiology Research Unit at the University of Liège, cautioned that a single helium detection does not constitute definitive proof of a substantial atmosphere. He stressed the need for reproducible signals before drawing firm conclusions about atmospheric composition. Ana Glidden, a postdoctoral researcher at MIT’s Kavli Institute, echoed this view, calling for further observations to resolve why helium was seen in 2024 but not in 2025.

CNN

• 2024 detection: Helium escaping was recorded during a transit.

Astronomy Magazine

• 2025 non-detection: Follow-up observations failed to see the same signal, suggesting atmospheric loss rates may vary with the host star’s activity.

CNN

A scheduled observation on September 23, 2024 will again capture a rare alignment of LHS 1140 b and its inner companion, providing an opportunity to compare atmospheric signatures under identical conditions. Planned spectroscopy with JWST aims to search for carbon dioxide, water vapor, and other molecules that could indicate habitability. Researchers also intend to monitor the host star’s X-ray and ultraviolet output to better understand its impact on atmospheric escape.

Scientists stunned: rocky planet’s atmosphere breakthrough could change everything for life