![]() "The evidence is interesting but has not quite really reached the threshold to incorporate into my mental register." "Death from space is always really cool," says Pincelli Hull, a paleontologist at Yale University. Even taken together, the effects are "not like the dinosaur extinction event-it's more subtle and local," says Brian Thomas, an astronomer at Washburn University who has studied the earthly effects of cosmic catastrophes for nearly 2 decades.įew astronomers are suggesting that the supernovae caused any great extinction at the time, and even fewer paleontologists are ready to believe them. In that way, the celestial event could have cooled the climate and helped initiate the ice ages 2.5 million years ago, at the start of the Pleistocene epoch. At the same time, atmospheric reactions triggered by the radiation could have led to a rain of nitrogen compounds, which would have fertilized plants, drawing down carbon dioxide. Tearing through the atmosphere, the particles would have also created pathways for lightning, perhaps kindling a spate of wildfires. A cosmic ray barrage might have boosted mutation rates by eroding Earth's protective ozone layer and generating showers of secondary, tissue-penetrating particles. In a flurry of studies and speculation, astronomers have sketched out their potential effects. 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. ![]() But the expanding fireball also accelerated cosmic rays-mostly nuclei of hydrogen and helium-to close to the speed of light. Its fusion fuel exhausted, the star had collapsed, generating a shock wave that blasted away its outer layers in an expanding ball of gas and dust so hot that it briefly glowed as bright as a galaxy-and ultimately showered Earth with those telltale atoms.Įrupting from hundreds of light-years away, the flash of x-rays and gamma rays probably did no harm on Earth. Over the past 2 decades, researchers have found hundreds of radioactive atoms, trapped in seafloor minerals, that came from an ancient explosion marking the death of a nearby star. But it left other traces, now coming to light. As the supernova faded over the following months, it probably also faded from memory. As luminous as the full Moon, it would have cast shadows at night and been visible during the day. For our Australopithecus ancestors who roamed Africa 2.5 million years ago, the bright new star in the sky surely would have aroused curiosity.
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