Summary
Over the past 2 decades, researchers have found hundreds of radioactive atoms, trapped in seafloor minerals, that came from an ancient supernova explosion marking the death of a nearby star. Erupting from hundreds of light-years away, the flash of x-rays and gamma rays probably did no harm on Earth. But the expanding fireball also accelerated cosmic rays—mostly nuclei of hydrogen and helium—to close to the speed of light. These projectiles arrived stealthily, decades later, ramping up into an invisible fusillade that could have lasted for thousands of years and might have affected the atmosphere—and life. In a flurry of studies and speculation, astronomers have sketched out their potential effects, including a depleted ozone layer, cancer-causing particles, wildfires, and a cooling of the climate that could have helped initiate the ice ages 2.5 million years ago. Most paleontologists are yet to be convinced, but astronomers argue that such supernovae could explain some extinction events that lack customary triggers like volcanic outbursts or asteroid impacts.
View Full Text