Supernova Explosions near the Earth

A supernova explosion within 10 parsecs of earth could cause a mass extinction. Over the past two decades,
deposits of the  live radioisotope iron 60 have been discovered on the ocean floor and on the Moon,
which point to supernova explosions within 50 parsecs of Earth during the past few million years.
Radioactive plutonium 244 has also been discovered recently, which may be due to a kilonova.
It is an open question whether a nearby astrophysical explosion might have caused a mass extinction in the past.