The search for life outside our solar system has taken another twist as researchers revealed they have discovered an atmosphere around an Earth-like planet 49 light years away that could have liquid water on its surface.
Atmospheres have previously been found around gas giant exoplanets as well as “sub-Neptunes”. There have also been signs of such envelopes around rocky exoplanets that sit outside their star’s habitable zone – a region in which liquid water could exist on the planet’s surface, and hence potentially support life.
But the new discovery is different.
“This is the first actually observationally confirmed atmosphere on a rocky planet in the habitable zone outside of our solar system,” said Dr Collin Cherubim, the first author of the study, who until recently was based at Harvard University.
The findings, he added, also marked the first direct identification of an atmospheric species for any rocky exoplanet, whether in a habitable zone or not.
“This is a really exciting discovery because I think it really puts LHS 1140b at the forefront as the best, most promising, exciting laboratory for studying astrobiology and habitability outside of our solar system,” he said.
The planet, LHS 1140b, has a mass 5.6 times that of Earth and its radius is 70% larger. While Cherubim noted it was similar to Earth in some ways – such as its overall composition and temperature – it differs in others: for example it is tidally locked, could have far more water, and probably has a very different atmosphere.
Discovered in 2017, it is relatively nearby and orbits a small red dwarf in the constellation of Cetus, the sea monster. This star is smaller and dimmer than our own sun but releases a greater proportion of its energy as ionising radiation.
Cherubim said as a result of the new study we now know LHS 1140b has all the ingredients for a habitable environment: a relatively rocky planet, a temperature that supports liquid water, and an atmosphere to prevent the water from escaping and to shield the planet’s surface from harmful radiation. In addition the star itself is quiet with few flares.
“So it’s a really exciting place to keep looking, especially to look for signs of life,” he said.
The team said no atmosphere was found around LHS 1140c – another rocky planet that orbits the same star.
Writing in the journal Science, Cherubim and colleagues reported how they observed LHS1140b as it passed in front of its star, using an infrared spectrograph mounted on the Magellan Clay telescope at Las Campanas Observatory in Chile.
Data captured in 2024 revealed helium that was escaping from the planet into space.
Cherubim said the team was able to rule out other possible explanations for the helium signal – including contamination from the Earth’s atmosphere.
Helium was not detected in observations of LHS1140b made in 2025. Cherubim described that as a shock, causing him – and others – to re-analyse the initial findings. “Every false positive we could think of, we have confidently ruled out,” Cheribum said.
Jayne Birkby, a professor of astrophysics at the University of Oxford, said the work was a fantastic discovery, adding that while small red dwarf planets were the most common type of star, and hence our best chance for studying nearby rocky exoplanets in their habitable zone, they were often very active – stripping away the atmospheres from the planets they host, leaving rocky planets with thin atmosphere or airless.
“That makes this discovery of an atmosphere surrounding LHS 1140b a crucial step towards understanding what it’s like living with a red dwarf,” she said.
“It’s fascinating that the signal varies too, it shows how the exoplanet’s atmosphere reacts to the high [extreme ultraviolet radiation] radiation of its host star, and may even tell us how this changes the planet’s surface conditions too,” she added. “It naturally leads one to ask if life could thrive here and if so what type of protective gear it would have had to evolve for itself.”
Dr Yamila Miguel of Leiden Observatory in the Netherlands also welcomed the results, adding it was already known that planets close to their host stars could lose atmospheric gases to space.
“What makes this planet so interesting is that it is losing enough of its atmosphere that we can actually detect it from here, which is not easy for a small, rocky planet,” she said.
Miguel noted the observations related to gas escaping from the planet’s upper atmosphere – rather than the lower atmosphere or regions close to the surface, where life would be expected to evolve.
“Therefore I do not think these results have any direct implications for detecting life on other planets,” she said.
