Contributed Talk - Splinter Education

Thursday, 21 September 2017, 14:20   (HS5)

Stable Atmospheres inside and outside the Solar System

S. Hohmann1
1 University of Siegen, Didactics of Physics, Observatory

The search for life on other planets is one of the most fascinating aspects in astrophysics, especially for learners of all ages. Recently, thousands of exoplanets - with an increasing number of terrestrial ones - have been discovered. This is leading to the question, if some of them are fit for life.
Usually, the habitable zone of a star is synonymous with the area, in which liquid water may be found. This aspect has a very "earth-bound" point of view - there is no proof, that life without water is impossible. But a long-time stable atmosphere is one (of the many) essential keys for the evolution of life.
This talk shows an estimation which allows to have a look at planets with different atmospheres surrounding stars with diverse luminosities and therefore diverse radiation pressures. If the radiation pressure predominates the gravity of a planet, the atmosphere cannot be stable for a long time. With the earth's atmosphere as a scale, one can assume, whether an atmosphere can exist long enough for the evolution of life or not.
This argument gives a lower limit for the necessary distance between star and planet fit for life. Most of the discovered exoplanets are quite close to their stars, caused by the methods of detection, so this estimation can be applied on a big part of them.