Astronomers have achieved a milestone in exoplanet science by detecting a helium-based atmosphere around LHS 1140b, a rocky exoplanet orbiting within the habitable zone of its parent star. The discovery, published in the journal Science, marks the first time researchers have confirmed an atmosphere on a rocky, Earth-like planet beyond the solar system, raising hopes for the eventual detection of biosignatures on similar worlds.
LHS 1140b lies approximately 48 light-years from Earth, circling a low-mass red dwarf star known as LHS 1140. The planet sits squarely in the habitable zone, the region where temperatures could allow liquid water to exist on the surface. While astronomers have previously identified numerous rocky exoplanets in such zones, none had shown clear evidence of an atmosphere until now.
Collin Cherubim, a doctoral candidate at Harvard University who led the research, described the planet as an “exotic weirdo” in a statement accompanying the study. “This is the first time anyone has detected an atmosphere on a rocky planet in the habitable zone of another star,” Cherubim said. “Twenty years ago, we wondered whether other Earth-like planets even existed. Then we found they are common and identified several in habitable zones. The next question was whether any of them had managed to retain an atmosphere.”
The detection was made using the WINERED near-infrared spectrograph mounted on the Magellan Clay Telescope at Las Campanas Observatory in Chile. The team took advantage of a rare alignment in which both LHS 1140b and another exoplanet in the same system transited across their star on the same night. While the companion planet showed no atmospheric signature, LHS 1140b revealed a clear outflow of helium, confirming the presence of an extended atmosphere.
Robin Wordsworth of Harvard University, one of Cherubim’s thesis advisors, noted the significance of the finding. “Now we know that at least one rocky exoplanet in the habitable zone has held onto its atmosphere,” he said. The detection validates a theoretical model Cherubim had previously developed, which predicted that LHS 1140b would host a high-altitude helium-rich atmosphere slowly escaping into space.
David Charbonneau, director of Harvard’s astronomy department, recalled being initially skeptical of Cherubim’s prediction. “Collin had analyzed the planets we knew and predicted this one would have a helium atmosphere,” Charbonneau said. “Then he organized telescope time, collected the data, and the detection turned out to be statistically impeccable.”
The presence of helium escaping from the planet suggests that its atmosphere has survived for more than three billion years, despite the intense radiation from its red dwarf star. In gas giants, strong stellar irradiation typically drives helium escape, but on rocky worlds the process may be slower. The researchers believe this longevity makes LHS 1140b an exceptionally valuable target for future observations, including potential searches for other atmospheric gases that could indicate biological activity.
The discovery addresses a long-standing puzzle in exoplanet science: why no atmosphere had been confirmed on any rocky exoplanet before. One possibility, the team suggests, is that in most such worlds the helium has already escaped entirely. LHS 1140b appears to be an exception, possibly due to its specific orbital history or planetary characteristics that allowed its atmosphere to persist.
LHS 1140b had previously attracted attention for the potential presence of a surface ocean. The new atmospheric detection adds another layer of intrigue, as an atmosphere is considered a fundamental requirement for surface liquid water and, by extension, for life as we know it. While the current study does not directly address habitability, it demonstrates that rocky planets in habitable zones can indeed retain gaseous envelopes, a prerequisite for more detailed astrobiological investigations.
The research team included scientists from Harvard University, the Carnegie Institution for Science, the University of California, Riverside, and other institutions. The study was published in Science under the title “Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone.”
Future observations using next-generation telescopes, such as the James Webb Space Telescope, could probe the composition of LHS 1140b’s atmosphere in greater detail, potentially identifying molecules like water vapor, carbon dioxide, or methane. For now, the detection of helium itself represents a breakthrough, proving that rocky exoplanets can hold atmospheres and opening a new chapter in the search for worlds beyond our own.