Science News9%
This “exotic weirdo” exoplanet has a rocky surface and an atmosphere 39%
By Lisa Grossman6%
7/16/2026, 6:00:00 PM
Keywords: Atmosphere, Exoplanet, Helium, Rocky Planet, M Dwarf, Habitable Zone, Lhs 1140b, James Webb Space Telescope
BS Summary: This article contains 24 faulty reasoning types, including Overconfidence Bias, Optimism Bias, and Biased Writer Voice, with Negativity Bias as the most egregious example at 13.9% saturation with 75 hits. Analysis detected 668 faulty-reasoning hits from 540 analyzed words, generating a BS Score of 44.8% and a BS Rank of 39% (12,905 of 21,167 articles). This article is better (less manipulative) than 61.00% of the article peer group.
For the first time, astronomers have detected an atmosphere around a rocky planet orbiting in the habitable zone of a nearby star.
Such planets have long been considered the best places in the galaxy to look for signs of alien life.
But so far, “the planets looked like bare rocks,” says astronomer Laura Kreid1berg of the Max Planck Institute for Astronomy in Heidelberg, Germany.
It wasn’t clear if planets like this could even have atmospheres.
This study shows that they can, astronomers report in Science July 16.
The planet, LHS 1140b, is about 5.6 times as massive as Earth and 1.73 times Earth’s size.
Those dimensions are consistent with an Earthlike composition shrouded in a gaseous atmosphere, or perhaps a global ocean of water.
It also orbits far enough from its star that its surface temperature could support liquid water.
But the host star is a cool, dim M dwarf, the most common type of star in the galaxy.
These stars produce notoriously bad neighborhoods, emitting harsh radiation and brutal stellar flares that could strip their planets’ atmospheres away.
“The open question is, can rocky exoplanets even keep their atmospheres around M dwarfs?”
says planetary astronomer Collin Cherubim of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
Cherubim and colleagues used the Magellan Clay telescope at the Las Campanas Observatory in Chile’s Atacama Desert to observe LHS 1140b passing in front of the star and blocking a bit of its light.
Just before this transit began and for a little while after, the researchers observed the molecular fingerprint of excess helium gas absorbing light from the star.
That excess is a sign of helium streaming away from the planet’s atmosphere, Cherubim says — which means it has one.
“Really, the most exciting thing here is that the planet has an atmosphere at all,” Cherubim says.
Previous studies had found signs of helium escaping from larger planets than LHS 1140b, called mini-Neptunes.
These may be in the process of losing their atmospheres, becoming bare rocks.
LHS 1140b is losing helium, too.
“It is slowly changing,” Cherubim says.
“On astronomical timescales, billions of years from now, the atmosphere will be quite different.”
But it probably won’t be lost forever.
LHS 1140b is cooler than the mini-Neptunes and is losing atmospheric mass at a much lower rate.
The planet has already held on to its atmosphere for more than 3 billion years and could be stable for a billion more, Cherubim calculates.
Even then, the planet could maintain an atmosphere made of heavier gases like carbon dioxide or nitrogen.
Follow-up observations with the James Webb Space Telescope will help determine other features of the atmosphere, like how much helium it contains and what other molecules are in there.
Another detection would also confirm the atmosphere is really there, Kreidberg says.
A rocky planet with a helium-rich atmosphere is a surprising finding, she adds.
“This is a kind of planet that we’ve never seen before,” she says.
Its atmosphere is thicker than expected for a rocky planet, but not thick enough to be a gas giant.
“Because it’s such an exotic weirdo planet, it never occurred to me to go look for it.”
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