Astronomers Confirm Atmosphere on Earth-Like Exoplanet LHS 1140b

The search for habitable worlds has long been compared to an astronomical Easter egg hunt, but a new study has identified a candidate that checks more boxes than previously observed targets. LHS 1140b, a planet 5.6 times the mass of Earth, is now the first rocky exoplanet confirmed to possess an atmosphere while orbiting within the habitable zone of its host star.

Observations at the Magellan Clay Telescope

The discovery emerged from data collected using an infrared spectrograph mounted on the Magellan Clay telescope at the Las Campanas Observatory in Chile. Researchers observed the planet as it transited, or passed in front of, its parent star—a red dwarf located in the constellation Cetus. By analyzing the light blocked during these transits, the team identified the presence of helium, a signature of an escaping atmosphere.

Lead author Dr. Collin Cherubim, who conducted the work while based at Harvard University, emphasized the precision required for these observations. The team’s computer models, developed by Cherubim, had predicted that such a planet would leak helium into space, a hypothesis that direct observations subsequently confirmed.

For more on this story, see Is Venus’ Atmosphere the Most Earth-Like Place in the Solar System?.

Habitability and the Red Dwarf Environment

LHS 1140b orbits a red dwarf star, a stellar type that makes up approximately three-quarters of the stars in our galaxy. These stars are typically smaller and cooler than our sun, but they are also known for extreme activity, including solar flares that can strip atmospheres from orbiting planets. The survival of an atmosphere on LHS 1140b over billions of years provides new evidence that rocky planets can endure these harsh conditions.

According to Space, the planet maintains a temperature suitable for liquid water, potentially creating a greenhouse effect that supports habitable conditions. Jayne Birkby, a professor of astrophysics at the University of Oxford, described the work as a fantastic discovery, noting that the planet’s atmospheric variation offers a rare window into how exoplanets react to extreme ultraviolet radiation from their host stars.

This follows our earlier report, Exoplanet GJ 3378b: Earth-like World Just 25 Light-Years Away, Mass Revised to 2.3x Earth.

Comparison of LHS 1140b and LHS 1140c

The research team also investigated other bodies in the same system to refine their understanding of planetary evolution. While LHS 1140b shows clear signs of an atmosphere, the team found no such evidence for LHS 1140c, a second planet orbiting the same star. The comparative data helps astronomers distinguish between planets that retain their envelopes and those that have been rendered airless.

By studying the rate at which helium is being lost from LHS 1140b, scientists are gaining insight into the planet’s underlying composition.

Read also: Super-Earth 25 Light-Years Away Could Host Alien Life.

Future Directions for Astrobiology

The scientific community views this discovery as a pivot point for astrobiology. While previous detections of atmospheres were largely limited to gas giants or “sub-Neptunes,” confirming an atmosphere on a rocky, Earth-like world provides a new laboratory for studying habitability outside our solar system. Researchers are now looking toward future observations to determine if other gases exist within the planet’s envelope.

Collin Cherubim, lead author, via Space

Despite the excitement, researchers maintain a cautious outlook regarding the surface conditions. While the presence of an atmosphere and the planet’s location in the “Goldilocks zone” are promising, scientists cannot yet say what the surface looks like or if it definitively hosts liquid water. The ongoing study of LHS 1140b remains a priority for understanding the potential for life in systems dominated by red dwarf stars.

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