Researchers led by University of Florida Assistant Professor of Astronomy Jason Dittmann used helium escape to probe the planet’s upper atmosphere. Their study, published in Science, reports evidence that helium is leaving the planet at a rate too high to be explained by a dwindling “leftover” helium reservoir alone.

The signal was captured with the Magellan Clay telescope at Las Campanas Observatory in Chile. To interpret why helium should be present despite the planet’s age, the team combined helium measurements with stellar energy conditions—specifically X-ray data that quantify how strongly the host star irradiates the planet.

That X-ray input matters because high-energy photons heat the upper atmosphere and can drive atmospheric particles upward until they escape. By linking the observed helium loss to the star’s X-ray luminosity, the authors infer that LHS 1140b must be replenishing helium continuously. Without such replenishment, helium would have largely vanished long ago.

This inference echoes atmospheric escape seen on Earth, but under markedly different stellar forcing. It also offers an important bridge between two ideas: that rocky planets can be largely airless, and that some may retain atmospheric components in a “steady-state” exchange with ongoing escape.

Dittmann originally discovered LHS 1140b in 2016 using ground-based transit searches. Because Earth’s own atmosphere can mimic or distort subtle dimming signals, he applied a machine-learning approach to distinguish planetary transits from terrestrial weather effects.

With JWST and Hubble’s ongoing “Rocky Worlds” observing efforts, the next steps focus on detecting molecules beyond helium. If signatures such as water vapor—or related carbon dioxide—emerge, it would strengthen the case for a stable atmosphere rather than an intermittent gas “burp” that rapidly evaporates.

The team expects that within roughly four to five years, observations will either confirm atmospheric persistence or push the planet toward a bare-rock interpretation. In either outcome, LHS 1140b is poised to become a flagship test case for how atmospheres survive around dwarf stars—and for whether the most Earth-like candidates truly stay habitable.

Keywords

Helium escape; LHS 1140b; rocky exoplanets; dwarf stars; habitable zone; atmospheric loss; X-ray irradiation; JWST; Hubble; machine learning

The planet, LHS 1140 b, is located about 48 light-years away and circles a cool red dwarf star. Because the habitable zone is defined by the temperature range where liquid water could exist on a surface, the finding elevates this target from “potentially rocky” to “atmospherically active.”

The study, published in Science, uses observational evidence of helium escaping from the planet’s upper atmosphere. Helium loss is a direct physical signature: when atmospheric particles are accelerated beyond the planet’s escape energy, they can stream away and imprint subtle absorption features in starlight during transits.

To test theoretical expectations, the researchers employed the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan Observatory in Chile. The approach hinged on a rare alignment: LHS 1140 b and another planet transited the same star on the same night, allowing the team to compare atmospheric signatures between worlds under nearly identical observing conditions.

In the resulting spectra, one planet showed no clear atmospheric evidence, while LHS 1140 b displayed the helium-related signal. The detection supports the interpretation that the planet maintains an atmosphere and that helium is gradually leaking into space.

Crucially, the helium atmosphere was not identified by assumption alone. It followed from a prior theoretical model predicting that LHS 1140 b could develop and sustain a helium-rich upper layer that escapes slowly. The observations provide the first strong empirical confirmation of that kind of atmospheric retention in a habitable-zone rocky planet.

The researchers estimate the atmosphere has likely persisted for more than three billion years. That longevity suggests the planet’s environment has remained stable enough for an atmosphere to endure, making it a compelling candidate for follow-up studies of surface conditions and possible ocean worlds.

Lead author Collin Cherubim emphasized that an atmosphere is essential for habitability as we understand it. He and collaborators now aim to determine the atmosphere’s broader composition and use their model to identify additional exoplanets with similar atmospheric escape signatures.

The work also points to a practical strategy for future surveys: monitoring escaping gases from ground-based telescopes may become a powerful way to characterize atmospheres on rocky planets that are otherwise difficult to probe.

Subject of Research: Atmospheric escape (helium) from a rocky habitable-zone exoplanet (LHS 1140 b)
Article Title: Escaping helium from a terrestrial planet atmosphere in a nearby habitable-zone
News Publication Date: 16-Jul-2026
Web References:
https://www.science.org/ (article hosted by Science)
References: Science (published article)
Image Credits: Melissa Weiss/CfA

Keywords: exoplanets, habitable zone, rocky planet, atmosphere detection, helium escape, LHS 1140 b, WINERED, red dwarf, transit spectroscopy, atmospheric retention