Modeling the Radiation-driven Mass Loss of Primary Atmospheres on Super-Earth-sized Planets

Since the discovery of the first extrasolar planets about only 30 years ago more and more planets have been found and analyzed. One of the most interesting findings about them was the fact that histograms of planets with radii between 1.5 and 2.5 Earth radii are less abundant than planets which are smaller or larger. This work investigates the possibility of photoevaporation as one of the main contributors to this particular pattern by using hydrodynamic modeling in combination with radiation transport to simulate planets with primary atmospheres that orbit close to their host star and hence experience strong ionizing radiation. The simulation results seem to support the hypothesis of photoevaporation one possible explanation to the existence of the radius gap. When there is no source of new gas the atmosphere erodes away with time depending on the star planet distance as well as the mass of the planet in a matter of several to dozens of millions years.