从一颗位于宜居带的邻近岩石系外行星大气中逃逸的氦气
Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone
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中文总结 AI 辅助
研究对LHS 1140b这颗位于宜居带的岩石系外行星进行光谱观测，通过近红外凌星光谱发现其大气有氦逃逸且随时间变化，解释结果与大气分馏模型一致，同一系统中更小且辐照更强的LHS 1140c未检测到氦吸收。
中文摘要 AI 辅助
对高辐照气态巨行星系外行星的观测表明有氦气从其大气中逃逸。岩石系外行星大气的证据有限，可能是因为它们已经逃逸。我们报告了对LHS 1140b的光谱观测，它是一颗在邻近低质量恒星宜居带轨道运行的岩石系外行星。近红外凌星光谱显示有氦气从行星大气中逃逸的吸收。在2024年检测到氦吸收，2025年未检测到，表明大气逃逸随时间变化。我们将这些结果解释为表明高层大气以氦为主且氢含量低，其他挥发性物质被困在较低高度，这与大气分馏模型一致。在同一系统中较小且辐照更强的LHS 1140c未检测到氦吸收。
英文摘要
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 spectroscopic observations of LHS 1140b, a rocky exoplanet that orbits in the habitable zone of a nearby low-mass star. The near-infrared 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 heavily irradiated exoplanet in the same system.
