Abstract Details
| Name: Sujan Sengupta Affiliation: Indian Institute of Astrophysics Conference ID: ASI2015_779 Title : Upper Limit on Extreme-Ultraviolet Luminosity of Stars Hosting Habitable Planets. Authors and Co-Authors : Sujan Sengupta, Indian Institute of Astrophysics, Koramangala 2nd Block, Bangalore 560034 Abstract Type : Oral Abstract Category : Stars, The Milky Way Galaxy and its neighbours Abstract : Habitable planets are rocky planets orbiting at such a distance from the parent stars that the surface temperature of the irradiated planet allows water to exist in liquid state. The habitability of a planet thus depends on the optical or bolometric luminosity of the star, the distance between the star and the planet and the physical properties of the planetary atmosphere. A good number of habitable planets has been discovered till date and many more are expected to be discovered in near future. However, owing to the lack of knowledge on the atmospheric properties, the ambient environment of such planets are unknown. It is known that sufficient amount of the Extreme Ultra-violet (EUV) radiation from the star can stripe out light atoms and molecules, in particular hydrogen from the upper atmosphere of a planet. If the rate of mass loss is sufficiently high then within a few billion years, substantial amount of hydrogen would escape causing the planet to become parched and hence inhabitable. Considering energy-limited hydrodynamical mass loss, an upper limit on the Extreme Ultraviolet luminosities of stars is derived which constrains the habitability of planets around them. Application of the limit to planet-hosting stars with known EUV luminosities implies that no M-type of star can have habitable planets around them. |