First atmosphere found on a habitable exoplanet
For the first time, astronomers have confirmed an atmosphere around a rocky planet sitting in another star's habitable zone - the region where temperatures could allow liquid water on the surface. The planet is LHS 1140 b, a super-Earth about 48 light-years away, and the discovery, published July 16 in Science, comes from a team led by Collin Cherubim, who completed the research as a doctoral student at Harvard.
The evidence isn't a photo or a spectrum bursting with oxygen and water. It's subtler: helium, quietly leaking from the planet's upper atmosphere into space. Using the Magellan Clay telescope in Chile, the team caught LHS 1140 b transiting its star the same night as a second planet in the system. That second planet showed no atmospheric signal at all. LHS 1140 b did - a clear, statistically solid detection of escaping helium.
"This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star," said Cherubim. The planet is about 5.6 times Earth's mass and 1.7 times its radius, orbiting a quiet, older red dwarf star every 24.7 days. Researchers estimate the atmosphere has survived for more than three billion years - a remarkably long time, in exoplanet terms, to hang on to your air.
The context
Here's the problem this discovery quietly solves: for decades, we've found rocky planets in habitable zones at a steady clip. What we haven't confirmed is whether any of them actually kept an atmosphere. Red dwarf stars - the most common type in the galaxy - are hard on nearby planets. They flare, blast out X-rays and ultraviolet radiation, and can strip a thin atmosphere away entirely, especially early in a planet's life.
So the open question wasn't "are there rocky planets in the right zone." It was "can any of them hold onto air long enough for that zone to matter."
The technique is what makes this result interesting beyond LHS 1140 b itself. Heavier gases like oxygen, nitrogen, or water vapor are faint and hard to detect, even for an instrument as powerful as JWST. Helium, though, escapes into a puffed-up, easier-to-spot halo as starlight heats the upper atmosphere. Cherubim had predicted this pattern mathematically before the observation - building a model of which planets should show helium signatures, then testing it. When the data matched, his advisor David Charbonneau, initially skeptical the approach would work, called the detection "statistically rock solid." This isn't just one lucky find - it's a validated method that can now be pointed at other candidates.
Psyll's perspective
It's worth being precise about what was and wasn't found, because exoplanet headlines tend to run ahead of the data.
Helium is chemically inert. It doesn't participate in biology, and its presence tells us nothing directly about life. What it does tell us is that the planet has retained a real, persistent atmosphere - something no rocky planet in a habitable zone had definitively shown before. That's a meaningfully different, more modest claim than "signs of life."
There's also an asterisk on the method itself: the escaping helium only reveals the upper atmosphere. Heavier molecules like water, carbon dioxide, or oxygen sit lower down, and the current data says nothing about them. It's entirely possible LHS 1140 b is a bare rocky world that occasionally "burps" gas which then escapes, rather than a planet with a stable, layered atmosphere. Notably, helium was detected in 2024 observations but not in a 2025 follow-up - a variability the team is still working to explain.
The next phase, using JWST and Hubble as part of a dedicated Rocky Worlds program, will hunt for water vapor and carbon dioxide at lower altitudes over the coming years. That's when we'll learn whether this planet resembles Earth in any meaningful way, or something stranger.
"At this point, we have absolutely no evidence for life on the planet," Cherubim noted. "But we think all of the really important, essential ingredients are there."
Not a second Earth, then - proof that the search for one just got a genuinely useful new tool.
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One question to sit with
If we eventually find water vapor in LHS 1140 b's lower atmosphere - but never find a biosignature - will that change how we think about Earth's improbability, or only deepen the mystery of why life happened here at all?