Astronomers have directly detected helium around LHS 1140 b, confirming that the rocky exoplanet has an atmosphere. The result marks the first direct atmospheric detection for a rocky planet located in the habitable zone of its star, according to the researchers.
LHS 1140 b lies 48 light-years from Earth and circles a red dwarf, a star smaller and cooler than the sun. Its orbit places it at a distance where temperatures could permit liquid water. That definition makes the planet an important target for studies of habitability, but it does not establish that water—or life—is present. Lead author Collin Cherubim explicitly said the team was not claiming evidence of life.
The planet was discovered in 2017 by a team led by Jason Dittmann, who is a co-author of the atmospheric study. Scientists already regarded the world as rocky and appropriately temperate. The new measurement adds another significant property: an atmosphere that includes helium. Researchers say other gases may also be present, but the available observations do not identify them.
The team tested a prediction from a planetary-evolution model developed by Cherubim. They observed LHS 1140 b with the Warm Infrared Echelle, or WINERED, spectrograph at the Magellan Observatory in Chile. As the planet passed in front of its star, starlight filtered through material surrounding it. The resulting spectroscopic data contained a helium signature. Another planet that transited the star during the same night did not produce a comparable result.
The detection also bears on a broader question about planets around red dwarfs. Such stars can remain active for long periods, emitting flares and other intense radiation capable of eroding planetary atmospheres. LHS 1140 b’s star is roughly 6 billion years old. The finding indicates that at least this rocky planet retained an atmosphere over billions of years, even though helium is still escaping from its upper reaches.
Researchers think the planet may contain substantial water, and an atmosphere could supply a greenhouse effect compatible with liquid water. Those possibilities remain to be tested. The observations do not reveal the surface or confirm habitability.
Follow-up work can search for additional atmospheric components and investigate whether water exists there. The immediate importance of the result is narrower but still consequential: astronomers now have a directly detected atmosphere on a rocky, habitable-zone exoplanet, giving future studies a concrete nearby system in which to examine how such atmospheres form, survive and evolve.
