Astronomers Report Possible Atmosphere on Rocky Exoplanet LHS 1140b from 2024 Observations

Astronomers recorded a spectral line in the light from LHS 1140b during 2024 observations that indicated excited helium atoms, which they interpreted as an atmospheric outflow leaking from the planet. Multiple reanalyses of the 2024 and 2025 data confirmed the helium line appeared only in the initial observations, while the same signature was absent in follow-up observations the following year.

Collin Cherubim at Harvard University and colleagues conducted the work, noting that measurements of escaping helium often vary or disappear over months and years. Sukrit Ranjan at the University of Arizona added that the signature remains poorly understood and can change with stellar activity or outflow shape.

LHS 1140b is described as a potential helium world with a thick atmosphere over a rocky or icy surface, where surface pressure could resemble conditions at the bottom of Earth’s ocean according to Natalie Allen at Johns Hopkins University.

Unpublished data from the James Webb Space Telescope may clarify the atmosphere’s size and composition. Cherubim said this planet has now become the best place to search for life outside the solar system, as no prior atmospheres had been detected on rocky, temperate exoplanets.

aea9708, and Cherubim plans to continue observing the planet to track any recurring signals.