Тип публикации: статья из журнала
Год издания: 2013
Идентификатор DOI: 10.1089/ast.2012.0957
Ключевые слова: Early atmospheres, Earth-like exoplanets, Energetic neutral atoms, Habitability, Ion escape, Low-mass stars, Stellar activity, hydrogen, article, astronomy, atmosphere, chemistry, heat, hydrodynamics, theoretical model, ultraviolet radiation, Hot Temperature, Models, Theoretical, Planets, Ultraviolet Rays
Аннотация: The recently discovered low-density super-Earths Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H2O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R-Earth and a mass of 10 M-Earth. We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. Key Words: Stellar activityLow-mass starsEarly atmospheresEarth-like exoplanetsEnergetic neutral atomsIon escapeHabitability. Astrobiology 13, 1011-1029.
Выпуск журнала: Vol. 13, Is. 11
Номера страниц: 1011-1029
ISSN журнала: 15311074
Место издания: NEW ROCHELLE
Издатель: MARY ANN LIEBERT, INC
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