In a landmark discovery for exoplanet science, astronomers have directly detected an atmosphere around LHS 1140 b — a rocky planet 48 light-years from Earth that orbits comfortably within its star's habitable zone. It is the first time an atmosphere has been confirmed on a rocky world where liquid water could exist on the surface.
The discovery, published in the journal Science, was led by Collin Cherubim, who recently earned his Ph.D. from Harvard University. The team used the WINERED spectrograph on the Magellan Observatory in Chile to observe the planet as it transited across its host star, a red dwarf about one-third the size of our Sun.
What the Atmosphere Reveals
The data showed a clear, undeniable signature of helium in the planet's upper atmosphere, slowly leaking into space. While helium escape is not unusual — even Earth's atmosphere slowly loses helium — the fact that LHS 1140 b has retained an atmosphere at all is remarkable. Red dwarf stars are known for intense stellar activity, with powerful flares that typically strip atmospheres from orbiting planets.
"This discovery is a big deal because it's showing that at least this rocky planet has retained an atmosphere over billions of years," Cherubim said. "It's a bona fide, robust way of saying yes, atmospheres can survive on rocky exoplanets."
The planet's host star is roughly 6 billion years old, meaning it has passed the age at which red dwarf radiation activity begins to calm down. This explains how the planet managed to hold onto its atmosphere.
A Planet That Checks Multiple Boxes
Discovered in 2017 by astronomer Jason Dittmann's team, LHS 1140 b has long been considered one of the most promising candidates for studying rocky exoplanet atmospheres. It is roughly 1.7 times the size of Earth and orbits close enough to its dim red dwarf star to maintain temperatures suitable for liquid water.
"It probably also has a lot of water," Cherubim noted. "If it has some amount of atmosphere that can provide a bit of a greenhouse effect, which we know it does now … it will very likely be what we consider to be habitable conditions on Earth."
The researchers caution that this does not mean the planet hosts life — but it does mean LHS 1140 b is now the most promising known candidate for further study. The planet is a primary target for NASA's James Webb Space Telescope, which could search for additional atmospheric gases including water vapor, methane, and carbon dioxide.
A Personal Scientific Journey
What makes the discovery especially compelling is that Cherubim first predicted this atmosphere using a theoretical model he developed entirely from scratch as a graduate student. He then used an observational technique typically reserved for gas giants and applied it to a rocky planet — something nobody had done before.
"I made this measurement that was actually consistent with my prediction, and it was really nice to kind of close the whole loop of the scientific method," he said.
The discovery represents the culmination of more than a decade of work since LHS 1140 b was first identified, and opens a new chapter in humanity's search for life beyond our solar system.
