For the first time in the history of exoplanet science, astronomers have confirmed the presence of an atmosphere on a rocky, Earth-like planet orbiting within the habitable zone of its star. The planet is LHS 1140 b, a super-Earth located approximately 49 light-years away in the constellation Cetus, with a mass of 5.60 Earth masses and a radius 1.73 times that of Earth. The detection, published in Science on July 16, 2026, was led by a team at the Carnegie Institution for Science, with contributions from the Harvard-Smithsonian Center for Astrophysics.
The evidence came not from a single observation but from a temporal comparison that is itself scientifically striking. Near-infrared spectroscopic observations detected helium escaping from LHS 1140 b's upper atmosphere in 2024 but that same helium signature was absent in follow-up observations taken in 2025. The implication is that the planet's atmosphere is not static; it is variable, potentially shaped by stellar wind interactions, magnetic field fluctuations, or volcanic outgassing cycles. This variability, reported by Carnegie and confirmed by Harvard's Center for Astrophysics, suggests a more complex atmospheric system than the thin, tenuous exospheres detected around some hot rocky worlds.
The significance of this detection extends well beyond a single data point. LHS 1140 b orbits a low-mass M-dwarf star, which are the most common stellar type in the galaxy. If a planet this close, 49 light-years, orbiting this type of star can retain an atmosphere despite the intense radiation environments typical of M-dwarfs, it substantially raises the statistical probability that habitable-zone rocky planets with atmospheres are common rather than exceptional. In the present age of AI, the detection "represents a milestone step toward the discovery of Earth-like rocky planets beyond our solar system.
The next step is atmospheric characterization determining what gases, beyond helium, compose LHS 1140 b's envelope, and whether any of them are consistent with biological activity. That work will likely require the James Webb Space Telescope or next-generation ground-based instruments. But the threshold question, does a rocky, habitable-zone world possess an atmosphere at all?, has for the first time, been answered.