A new type of Goldilocks zone for life

The biggest extinction in history was the Permian-Triassic event (more of a phase, actually) and it may have been caused by a supernova. It set life on Earth back in a huge way: it took many millions of years for the diversity of life to bounce back. Think about that: millions of years. Biologically modern humans have only existed for a couple million years, and argiculture has only been around for about 10,000, a sliver of a fraction of a percent of the time it took life to get its groove back after the P-T extinction.

Over 96% of sea species, and 75% of land species went extinct over about 60,000 years. Ecosystems did not recover for millions of years. These numbers actually underestimate the devastation, as these are the loss of species. But if you look at individual creatures, almost everything on Earth died, which just the slightest residue of life left.

If the PT wipeout was caused by a supernova — and it’s definitely plausible — that suggests an interesting new type of Goldilocks zone for life in the cosmos: star systems in rural galactic halos might be a safer place for life to grow up, far from the madding crowds of stars closer to galactic cores. What looks like the “edge” of a galaxy in photos is really just the end of thick clouds of gas and dust and the fiercely hot and bright young stars they are constantly forming in them… and blowing up. There are lots of calmer, dimmer stars systems way further out than that.

(I love this combination of astronomy and paleontology.)