Earth, I mean. A recent paper on the role of GRBs on life extinction in the Universe uses recent data on gamma ray bursts to calculate how likely a sterilization event is, both here and elsewhere. Intense bursts of gamma rays are released when compact binary stars merge (shorter bursts) or when massive stars die (longer ones). How likely is it that a gamma ray burst near the earth has released a sterilizing dose of radiation?
Amongst the different kinds of GRBs, long ones are most dangerous. There is a very good chance (but no certainty) that at least one lethal GRB took place during the past 5 Gyr close enough to Earth as to significantly damage life. There is a 50% chance that such a lethal GRB took place during the last 500 Myr causing one of the major mass extinction events.
Why do these bursts have the potential to damage life? The gamma rays lead to nitric oxide formation, which then depletes the ozone. Without the protecting mantle of ozone UVB levels rise, damaging life on land and near the surface of the oceans. Loss of planktonic life leads to loss of other marine life.
Is life everywhere in the galaxy this harassed? No, in most of the Milky Way it's much worse. We are out toward the edge of the galaxy, just shy of where the stellar dust is too thin in metals to form complex molecules. Most of the stars in the galaxy are closer to the core and the higher density of stars means a greater chance for a devastating long gamma ray burst.
We find that the probability of a lethal GRB is much larger in the inner Milky Way (95% within a radius of 4 kpc from the galactic center), making it inhospitable to life. Only at the outskirts of the Milky Way, at more than 10 kpc from the galactic center, this probability drops below 50%.
Wait! It gets worse! Not only are we in a good neighborhood within our own galaxy, our own galactic neighborhood is sparse enough to protect us as well. Most galaxies and stars are in the denser parts of the universe. That higher density means more gamma ray bursts. How lucky are we?
When considering the Universe as a whole, the safest environments for life (similar to the one on Earth) are the lowest density regions in the outskirts of large galaxies and life can exist in only ≈ 10% of galaxies.
The authors ominously close with "the damaging nature of GRBs could help explain
Fermi's paradox."
One more thing to be grateful for.