Super-Earth LHS 1140b Shows Potential Atmosphere, Boosting Life Search
Scientists detected promising signs of an atmosphere on super-Earth LHS 1140b, located 49 light-years away in its star's habitable zone. This finding significantly enhances its potential for supporting life.
ATLANTA — Astronomers have identified compelling evidence suggesting that a 'super-Earth' exoplanet, designated LHS 1140b and situated 49 light-years from our solar system, may possess an atmosphere. This discovery significantly elevates its potential as a candidate for extraterrestrial life, as it orbits within the habitable zone of its star.
LHS 1140b, approximately five times the mass of Earth, orbits its star at a distance that allows for surface temperatures conducive to liquid water. Researchers believe the planet is primarily rocky, with characteristics similar to Earth, potentially including an iron core and silicate mantle, along with a less dense component possibly comprising water and an atmosphere. Collin Cherubim, a planetary scientist and lead author of the study published in the journal Science, stated that the planet's mass and radius measurements indicate a density consistent with a rocky world, possibly retaining a primordial atmosphere.
The search for atmospheres on rocky exoplanets is a challenging endeavor. Astronomers typically must wait for a planet to transit, or pass in front of, its host star. During this transit, starlight filtering through any potential atmosphere can reveal chemical signatures. While previous atmospheric detections have been made on gas giant exoplanets, confirming an atmosphere on a rocky world in the habitable zone would be a landmark achievement.
Assessing Atmospheric Composition
Cherubim, a NASA Sagan Fellow at the University of Chicago, developed a model hypothesizing that many planets initially form with atmospheres rich in hydrogen and helium. As these planets evolve into rocky bodies, they might shed much of their hydrogen but retain helium, a slightly heavier element. By applying this model to known exoplanets, Cherubim identified LHS 1140b as a promising candidate. Observations using the Magellan Clay telescope in September 2024 detected helium escaping from the planet, a key indicator for the presence of an atmosphere.
"We believe LHS 1140b is in that sweet spot, where it lost its hydrogen and it kept its helium, which is now slowly escaping," Cherubim explained. While helium alone may not support life, it suggests the possibility of other, more life-sustaining gases being present. "We don't have any other detections of any other molecules in the atmosphere yet, but I'm optimistic," he added. "I would go ahead and bet that we will find something eventually." This finding is particularly significant given that LHS 1140b orbits a red dwarf star, the most common type of star in the galaxy. Though red dwarfs present challenges due to their high activity levels, their smaller size and cooler temperatures make atmospheric studies of orbiting planets more feasible.
The potential for rocky planets to retain atmospheres around active red dwarf stars has been a long-standing question in astronomy. "Can rocky planets have atmospheres around red dwarfs? This is the first bona fide yes," Cherubim asserted. "It's kind of a sigh of relief for a lot of us. But the jury's still out. Maybe this is a weird planet, and it's an oddball, or maybe it's the first of many."
Follow-up observations in 2025 did not detect helium, a puzzling outcome that researchers attribute to variability in the escape rate, possibly dropping below the instrument's detection threshold. This mystery is now a focus of ongoing research. The team plans further observations with advanced instruments, including the James Webb Space Telescope, to confirm the presence and composition of the atmosphere.
Jason Dittmann, an assistant professor of astronomy at the University of Florida and a co-author of the study, expressed relief and excitement. "So I think finding a positive example of a rocky planet with an atmosphere is really significant. It's what we've been hoping to find for years," Dittmann stated. "What else is there besides helium? Can we maybe find water next? Something else?" The prospect of studying multiple rocky planet atmospheres is opening new avenues for comparative planetology.
Other researchers, like Ana Glidden at MIT, highlight that while LHS 1140b's orbit around a relatively quiet star and its super-Earth status favor atmosphere retention, further observations are critical. Michaël Gillon, a research director at Belgium's University of Liège, urged caution, noting that the single helium detection requires more robust confirmation and reproducibility before definitive conclusions can be drawn about the planet's atmosphere.