Astronomers have for the first time detected an atmosphere surrounding a rocky, Earth-like planet located within the habitable zone of another star, marking a significant advance in the search for extraterrestrial life. The discovery centers on the exoplanet LHS 1140 b, which orbits a red dwarf star approximately 49 light-years from Earth in the constellation Cetus. The findings were detailed in a study published July 16 in the journal Science.

LHS 1140 b, identified nearly a decade ago, lies within the so-called "Goldilocks" zone, where conditions may allow liquid water to exist on the planet’s surface—an essential factor for supporting life as understood on Earth. The planet orbits its host star, LHS 1140, an M dwarf that is smaller and much less luminous than the sun. These types of stars are the most common in the galaxy but emit high levels of X-ray and ultraviolet radiation, which can strip away planetary atmospheres, raising questions about the survivability of atmospheres on planets orbiting them.

Lead author Collin Cherubim, who recently completed his PhD in Earth and planetary sciences at Harvard University and led the research, stressed the significance of the detection. “An atmosphere is essential for a planet to support life as we know it,” he said, noting that previous observations had not conclusively identified atmospheres on rocky exoplanets in habitable zones.

Using computer models, Cherubim predicted that LHS 1140 b would possess a helium-dominated atmosphere. The research confirmed the presence of helium, making it the only gas robustly identified so far. The model also suggests the atmosphere likely contains water vapor, carbon monoxide, carbon dioxide, and smaller amounts of dioxygen, although the presence of water remains a prediction aligned with climate simulations of the planet’s conditions.

Despite some surface similarities to Earth and its place in the habitable zone, the planet’s atmosphere is expected to differ substantially from Earth’s, with a composition dominated by helium rather than nitrogen or oxygen. According to Cherubim, this suggests LHS 1140 b may represent an entirely new class of volatile-rich "helium world," with oxidizing gases present but at atmospheric layers not yet probed by current observations.

While the detection marks a milestone, Cherubim cautioned against assuming that the atmosphere is breathable or that the planet is necessarily habitable for humans. The high-energy radiation from the host star and unusual atmospheric composition likely create conditions unlike those on Earth.

Although other rocky exoplanets have been found within habitable zones, this study is the first to provide clear evidence of a stable atmosphere existing over billions of years on such a world. This breakthrough opens new avenues for investigating the potential for life on planets orbiting around common, yet challenging, M dwarf stars.