When stars run out of fuel, they can collapse under their own gravity, exploding as supernovae that blast debris and radioactive nuclei far into space. Most of these events are too far from Earth to affect our planet. But if one happened nearby, the effects could be dramatic.
By studying radioactive isotopes on Earth, scientists have uncovered evidence suggesting two near-Earth supernovae occurred in the past few million years. Some researchers now hypothesize that supernova-generated particles known as cosmic rays might have depleted the ozone layer, increased cancer rates in ancient organisms, sparked wildfires, and even started an ice age.
Source: Science Mag