2026-07-16 ハーバード大学
＜関連情報＞
- https://current.fas.harvard.edu/stories/harvard-scientists-detect-atmosphere-distant-earth-planet
- https://www.science.org/doi/10.1126/science.aea9708
居住可能領域を周回する近隣の岩石系外惑星の大気からヘリウムが放出される Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone
Collin Cherubim, Shreyas Vissapragada, Tim Cunningham, Annabella G. Meech, […] , and Mercedes López-Morales
Science Published:16 Jul 2026
DOI:https://doi.org/10.1126/science.aea9708
Abstract
Observations of highly irradiated gas giant exoplanets have shown helium escaping from their atmospheres. There is limited evidence for atmospheres on rocky exoplanets, perhaps because they have already escaped. We report near-infrared spectroscopic observations of LHS 1140b, a rocky exoplanet that orbits in the habitable zone of a nearby low-mass star. The transit spectra show absorption by helium escaping from the planet’s atmosphere. Helium absorption is detected in 2024 but not in 2025, indicating time-variable atmospheric escape. We interpret these results as indicating an upper atmosphere dominated by helium and depleted in hydrogen, with other volatile species trapped at lower altitudes, consistent with atmospheric fractionation models. No helium absorption is detected for LHS 1140c, a smaller and more strongly irradiated exoplanet in the same system.
