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Amedeo Balbi – Università di Tor Vergata, Roma


It is generally thought that the habitability of a planet is strongly influenced by the amount of ionizing radiation incident on its atmosphere and surface. While the host star is usually the prevalent origin of such high-energy radiation, previous studies have also considered the effect on a hypothetic biosphere of other possible sources, in particular with regard to potentially catastrophic transient events such as nearby gamma ray bursts or supernova explosions. Here we consider a phenomenon whose astrobiological consequences are much less explored, i.e. the production of X-ray and extreme ultraviolet (XUV) radiation during the peak of the active phase of supermassive black holes. In particular, we investigated how the activity of the supermassive black hole at the center of the Milky Way, known as Sagittarius A* (Sgr A*), may have affected the habitability of Earthlike planets in our Galaxy. Our results show for the first time that the combined effect of atmospheric loss and of the direct biological damage to surface life was probably significant during the AGN phase of Sgr A*, possibly hindering the development of complex life within a few kiloparsecs from the galactic center.

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