Photoevaporation
Photoevaporation (literally evaporation due to light ) describes a process in which a planet is robbed of its atmosphere or its components by the action of high-energy photons .
Basics
All masses, including planets, have an escape speed that has to be reached in order to completely leave the gravitational sphere of influence of the mass or the planet. By bombarding the atmosphere with high-energy photons, e.g. B. UV or X-rays , particles in the atmosphere are accelerated (heated) by ionization so that they can reach the required escape speed and leave the planet.
The lighter the particles, the higher the speed that ionization gives them. Therefore, hydrogen , whose atoms with mass number 1 and whose molecules with mass number 2 are the lightest, is the first gas to leave the planet during photoevaporation.
Photoevaporation in protoplanetary disks
Protoplanetary disks can be dispersed by photoevaporation (see figure). However, a strong influence of photoevaporation can only be determined if there is sufficiently strong radiation. This is especially the case near O and B class stars. Since the protoplanetary disks consist of gas and dust , the photoevaporation of the lightest gases such as hydrogen and helium can influence the composition of the developing planet.