恒星物理研究组知识库

近轨道~①系外行星受到其宿主恒星强烈的X射线和极紫外(X-ray and Extreme Ultraviolet,XUV)辐射。恒星辐射可能会使富气体行星的气体摆脱行星的引力束缚而逃逸到行星的洛希瓣外。随着XUV辐射的增大,行星的大气逃逸可由较缓和的金斯逃逸变为剧烈的流体动力学逃逸。随着空间望远镜和地面望远镜的发展,在一些行星周围发现了膨胀的H,He,C,O,Na和Mg等元素的大气。行星大气研究从最初的紫外波段探测,已经发展到光学波段和近红外波段的探测。理论上,系外行星大气逃逸的流体动力学模型也已相继建立起来。这些模型涉及到行星大气的光化学、恒星风与行星风的相互作用、恒星辐射压以及行星磁场等方面。然而,一个包含所有过程的复杂模型还有待建立。

Exoplanets with orbits close to their host stars receive strong XUV (X-ray and extreme ultraviolet) radiation from the stars. For gas planets, the XUV may lead to the gas overcome the planets' gravitational potential and thus escape from the planet. With the increase of XUV radiation, the escape process of the atmosphere can change from the relatively moderate Jeans escape to a severe fluid dynamic escape. On the observational side, with the development of space telescope and ground telescope, some planets with the expanded atmospheres of hydrogen, helium, carbon, oxygen, magnesium, and possibly sodium have been observed. The detection of exoplanetary atmosphere starts from UV band,
and it now approaches to the optical and near infrared band. On the theoretical side, fluid dynamics models of exoplanets' atmospheric escape are built, some of which (individually or part) include processes such as photochemistry, interaction of stellar wind and planetary wind, stellar radiation pressure, planetary magnetic field etc. However, a complete model containing all the important processes has yet to be established.