Scientists discover the first confirmed atmosphere around rocky planet outside our solar system that is within the habitable zone
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,” Cherubum 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.
Quelle: The Guardian
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Astronomers discover 1st atmosphere around a rocky Earth-like planet in the habitable zone
"It's in the habitable zone, which is super exciting for astrobiology and habitability and searching for life."
This might be the closest we've gotten to finding a planet that could support life: Astronomers have detected an atmosphere around an Earth-like, rocky planet orbiting in the habitable zone around its star, a monumental first.
The rocky planet, called LHS 1140 b, is 48-light-years away from Earth and according to this new research, it has an atmosphere that contains helium. It is also the first rocky planet to have an atmosphere be detected directly. This is the first rocky planet to be found with an atmosphere that is also in the habitable zone, meaning it's at the right distance away from its star for liquid water to potentially exist on the planet. As we continue to search the cosmos for planets that can be considered "habitable," this planet checks more boxes than almost anything we've ever seen.
"We have actually detected directly the helium present in the atmosphere itself, and that's the first direct detection for any rocky exoplanet, which is really exciting … and then there's this added bonus that it's in the habitable zone, which is super exciting for astrobiology and habitability and searching for life," lead author Collin Cherubim, who recently earned his Ph.D. from Harvard University, told Space.com. "It feels kind of surreal."
What's this planet like?
Let's explore this planet and the system where it "lives."
This exoplanet, or planet outside of our solar system, was first discovered in 2017 by a team led by astronomer Jason Dittmann who is now a co-author on this new discovery.
"This planet was found like 10 years ago, and we're just now saying, okay, that's an atmosphere," Dittman told Space.com. "We're slowly narrowing the gap and checking these boxes … we're finding a planet that's rocky, a planet that's of the right temperature and now … it's like okay, we finally found one that has an atmosphere."
And being a rocky planet, "there's definitely a surface … it's made of rocks," Dittman said. What does the planet's surface look like? We can't say yet, but the researchers who found this planet's atmosphere think there's a good chance it could have water.
While it orbits a red dwarf star, which is smaller and cooler than the sun, it orbits closer than we do to our star, maintaining a temperature that keeps the planet in the "Goldilocks zone" where liquid water could exist on its surface.
"It probably also has a lot of water," Cherubim said. "If it has some amount of atmosphere that can provide a bit of a greenhouse effect, which we know that it does now … it will very likely be what we consider to be habitable conditions on Earth, and conditions that would likely support liquid water."
So is it Earth-like? While it's certainly not an Earth copy, this planet can be considered Earth-like in two main ways, Cherubim shared. One: its overall composition. The planet is rocky, likely with an iron core and (now we know) it has an atmosphere. And two: the planet's temperature is just right for liquid water, which is necessary for life at least as far as we understand it on our planet.
Finding an atmosphere
The discovery of the first exoplanet was confirmed just over 30 years ago. Since then, scientists have found over 6,000 exoplanets and counting. And while a few rocky planets have been found in their star's habitable zone, it wasn't until now that an atmosphere has been confirmed around a rocky planet in the habitable zone.
One reason why scientists have had a hard time finding such planets with atmospheres is their stars. LHS 1140 b orbits the most common type of star, a red dwarf, which is about one-third the size of our sun. This type of star remains active for a lot longer than stars like our sun. This activity means it releases bursts of extreme radiation like solar flares and coronal mass ejections. And typically, the extreme radiation around these stars totally strips the atmospheres from the planets orbiting them, so astronomers have wondered if planets orbiting these stars can have an atmosphere at all.
"This discovery is a big deal because it's showing that at least this rocky planet has retained an atmosphere over billions of years," Cherubim said. It's "a bona fide, robust way of saying yes, atmospheres can survive on rocky exoplanets."
It's possible that other gases beyond helium are in the planet's atmosphere, and it's possible that some of its atmosphere was previously stripped away by its star's radiation. But the red dwarf that this planet orbits is roughly 6 billion years old, a few billion years older than the age at which their extreme radiation activity begins calming down. So while some helium is still slowly escaping the planet's atmosphere over time, the team expects the planet to retain an atmosphere, Dittman shared. After all, even Earth's helium is slowly escaping our own atmosphere.
The proof is in the atmosphere
To prove that this planet has an atmosphere, the team started with a prediction that Cherubim made during graduate school. It all started with a theoretical model and a sneaking suspicion that there must be rocky exoplanets with atmospheres other than Earth.
"This came out of a very specific prediction from a planetary evolution model that I actually developed myself, from scratch, from first principles, for my Ph.D. as a theorist, and I made a very specific prediction about this planet," Cherubim said. "And then I went out and did a pretty unexpected, weird thing using this technique that's typically reserved for observing giant planets, and I used it for a rocky planet, which nobody has done before.
"And lo and behold, I made this measurement that was actually consistent with my prediction. And it was really nice to kind of close the whole loop of the scientific method."
The team took the theoretical model that Cherubim developed in graduate school and put it to the test using the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan Observatory in Chile. And with their observations, they were able to see LHS 1140 b and another planet both transit, or pass in front of, their star in the same night. With this spectrographic data, they could identify the signatures of molecules in the atmospheres of these planets as they passed in front of the star. And while one planet yielded no results, this planet showed a direct, undeniable helium signature.
Are there aliens?
When looking at a planet that is rocky, has an atmosphere, and is in the habitable zone (meaning it could have liquid water), the question of life comes up quite quickly.
But the researchers don't have enough data to make that conjecture. "I'm not claiming this planet has life," Cherubim made clear. With further investigation, scientists could better understand what else might be in this planet's atmosphere, and they could confirm if it has water. Further observations might not be able to confirm habitability or identify any life on the planet, but they could at least help us to better understand planets like this.
With this being the first planet of its kind discovered, further exploration will help us to put the pieces together. But it is certainly a major step forward in the eternal human quest to answer the question: are we alone?
