For years, astronomers hunting for a second home for life have collected the ingredients one at a time: a rocky world here, the right temperature there, water somewhere else. Now, for the first time, they have found those pieces together on a single planet — and confirmed that it holds onto an atmosphere.
The world is LHS 1140b, a planet roughly 48 light-years away in the constellation Cetus. In a study published in the journal Science, a team led by Collin Cherubim, who recently completed his doctorate at Harvard University, reported the first observational confirmation of an atmosphere around a rocky planet sitting in its star's habitable zone — the band of orbits where liquid water could persist on a surface.
"This is the first actually observationally confirmed atmosphere on a rocky planet in the habitable zone outside of our solar system," Cherubim said, adding that identifying an atmospheric species there is a first for any rocky exoplanet. That species is helium: researchers detected the gas escaping from the planet's upper atmosphere, a hydrogen-poor envelope in which heavier compounds such as water are thought to be trapped closer to the surface.
A decade of narrowing the search
LHS 1140b is no twin of Earth. It carries about 5.6 times our planet's mass and is some 70 percent wider, and it is tidally locked, keeping one face permanently toward its star. That star is a small, cool red dwarf — dimmer than the Sun but, crucially, quiet, with few of the violent flares that can strip a planet bare.
The planet was first spotted in 2017 by a team that included Jason Dittmann, now a co-author on the new work. "We're slowly narrowing the gap and checking these boxes," Dittmann said, describing how the object has gone from a promising dot to a rocky, temperate world with a confirmed atmosphere. A sibling planet in the same system, LHS 1140c, showed no such envelope.
Why it matters: an atmosphere does more than tick a box. It can shield a surface from radiation and keep water from boiling off into space — conditions life would need. None of this proves LHS 1140b is inhabited. But it hands scientists their most promising nearby laboratory yet for asking whether we are alone.