Researchers from Harvard University reported an atmospheric signature around LHS 1140 b, a rocky exoplanet orbiting a red dwarf about 48 light-years from Earth. The planet lies in its star’s habitable zone, where liquid water could be possible under suitable atmospheric conditions. That designation does not establish surface habitability or life. LHS 1140 b is larger and more massive than Earth and is classified as a super-Earth, a category that describes its size rather than proving an Earth-like composition. The findings were published in Science.
The team used the WINERED spectrograph at the Magellan telescope in Chile to observe helium escaping from the planet’s upper atmosphere. During an unusual observing chance, LHS 1140 b and another planet in the same system crossed their host star on the same night. The comparison transit showed no atmospheric signal, while LHS 1140 b showed helium consistent with an escaping upper atmosphere. This observation traces an extended, evaporating atmospheric layer; it is not a complete inventory of the planet’s atmosphere or a direct measurement of gases closer to the surface.
Lead researcher Collin Cherubim, a Harvard doctoral researcher, described the result as “the first atmosphere discovered on a rocky planet in the habitable zone of a star outside of our solar system.” Harvard researchers David Charbonneau and Robin Wordsworth were also identified as study leaders. The team’s helium interpretation was anticipated by a theoretical model. The observation shows how ground-based transit measurements can help investigate the atmospheres of small exoplanets.
Researchers aim to determine the atmosphere’s broader composition and distinguish between possible atmospheric and interior models, including water-rich and heavier-molecule scenarios. The presence and abundance of lower-atmosphere gases remain open questions. Water vapor and carbon dioxide are among the possibilities; methane is another. A liquid-water ocean is one possibility under discussion, not an observed feature. Atmospheric spectra and information about the planet’s mass and radius, combined with data on its star and climate models, will help constrain its structure and conditions.
The reported helium escape does not establish that LHS 1140 b supports life or has an Earth-like climate. Instead, the finding makes the planet a high-priority target for follow-up observations and shows how researchers can study atmospheric escape from rocky worlds. Detecting helium in the upper atmosphere can help researchers investigate how a planet’s atmosphere evolves. Further observations will be needed to assess whether heavier gases persist beneath it.
The research also adds to efforts to understand how atmospheres form and endure around planets beyond our solar system. LHS 1140 b’s location in the habitable zone makes it scientifically compelling, but its habitability depends on its atmosphere’s composition and ability to persist. Internal structure also matters, as do stellar irradiation and activity. Future observations will test competing models and help establish what conditions, if any, may exist on this distant super-Earth.
