The search for extraterrestrial life is surely one of the most important tasks we humans can undertake. However, the cosmos is vast and we don’t really have any idea which bits of it are actually habitable. But what if we could target the search? We have built the first-ever “cosmobiological” model mapping the galaxies in our local universe to help us understand which ones are habitable. Surprisingly, we found that our own galaxy was not one of the top candidates.
Ingredients for Habitability
Drawing on our understanding of habitable zones within a galaxy, we proposed that the overall habitability of any galaxy depends on three key astrophysical criteria. One is simply the total number of stars capable of hosting planets, which is roughly related to the size of the galaxy. Another is the total amount of the building blocks of planets and life – such as carbon, oxygen and iron – the so-called astrophysical “metals”. Another is the negative influence of supernova explosions, whose powerful (and poisonous) radiation could potentially inhibit the formation and evolution of complex life on nearby planets.
