Galactic cosmic-rays and habitable planets

The question if there is life on other planets has fueled a decade full of exciting discoveries in the field of exo-planet research. The number of known exoplanets has grown beyond 5,000 till today and with the launch of the James Webb Space Telescope, we are now able to probe the atmospheres of the most nearby systems directly, allowing to search for tracers of life. However, most of the current approaches of finding life are based on a “follow-the-water” strategy. Here, we present a different approach by studying the impact of Galactic cosmic-rays (CRs) on potentially habitable planets around Sun-like stars. Most of the CRs that interact with the Earth’s atmosphere originate directly from the Sun. Due to their low-energy they get absorbed high in the atmosphere and contribute little to the radiation-dose we receive at the surface. On the other hand, the Galactic CR spectrum extends to much higher energies allowing the particle-induced cascades to reach ground level and directly impact life. The detection of very-high energy gamma-ray emission from stellar clusters has increased number of source classes known to accelerate cosmic-rays at least up into the TeV domain to four. We use observational data of the gamma-ray emission from Supernova remnants, colliding-wind binaries, young and massive stellar clusters and the Galactic center to infer the CR density around these sources and determine distances up too which life gets affected by the produced CRs for a “twin” of our solar system.