Astronomy
First confirmed atmosphere around a rocky planet in the habitable zone
LHS 1140 b is a rocky planet about 48 light-years from Earth, 1.6 times the mass of our world, and it orbits inside its star's habitable zone — the band where liquid water could exist on a surface. For years it was one of the most promising places to look for life elsewhere. The hard part was proving it even has an atmosphere at all. That is now settled: astronomers have detected one.
How they found it
When a planet passes in front of its star, a thin slice of the star's light threads through the planet's atmosphere on the way to Earth. Different gases absorb different colours, leaving fingerprints in the spectrum. The team analysed those fingerprints using observations from the European Southern Observatory's Very Large Telescope and its CRIRES+ infrared spectrograph.
What they found is helium — and they found it in a tellingly uneven way. In 2024, the helium absorption signal was there; in 2025, it was gone. That change over time is the key. False positives from starlight or distant gas do not typically turn on and off between orbits, so the time-variable signal points to the planet's own atmosphere, actively losing material.
Why this is a first
Roughly half of nearby stars have planets the size of Earth or a bit larger. Until now, no rocky planet sitting in its habitable zone had a confirmed atmosphere. Some smaller rocky worlds appear bare rock; others, closer to their stars, seem stripped clean by stellar winds. LHS 1140 b shows that a rocky, temperate planet can keep an atmosphere intact.
Helium itself is not the air a planet would breathe — it is a light gas escaping into space. But its presence is the smoking gun that a denser atmosphere, possibly built from molecular nitrogen and carbon dioxide, is underneath. Finding helium is the first step; measuring the bulk composition is the next.
What it changes
The result narrows the field of candidates worth detailed follow-up. Before this, every habitable-zone super-Earth was a question mark; now at least one is a known atmosphere, giving telescopes a real target to study in depth. It also informs how we model the other side of the question: planets that have no atmosphere, and whether their absence is the norm rather than the exception.
For the search for life, an atmosphere is a prerequisite. It stabilises a climate, shields a surface from radiation, and can hold water in the air. LHS 1140 b does not prove habitability, but it removes the most basic doubt — that the planet is a dead, airless rock.
Knowledge takeaway: LHS 1140 b, a 1.6-Earth-mass rocky planet 48 light-years away, has the first confirmed atmosphere of any rocky planet in the habitable zone. Time-variable helium absorption — present in 2024, absent in 2025 — distinguishes a real planetary atmosphere from false signals. The detection gives life-hunters a verified target to study with future telescopes.