Supernovas may have triggered ancient ice ages, wiping out 60–70% of Earth’s species: Study

Most people know the theory that an asteroid wiped out the dinosaurs 66 million years ago. But Earth has faced at least five mass extinctions, and not all were caused by space rocks. Scientists now suggest that two of these cataclysmic events — one 372 million years ago and another 445 million years ago — may have started with dying stars light-years away.  

A new study, based on a census of stars in the Milky Way, indicates that these ice ages might have been triggered by nearby supernovas.  

"If a massive star were to explode as a supernova close to the Earth, the results would be devastating for life on Earth," said Nick Wright, an astrophysicist at Keele University in the UK. "This research suggests that this may have already happened."  

The late Devonian and Ordovician mass extinctions remain mysteries. The Ordovician event is believed to have wiped out about 60% of invertebrate sea creatures when most life was in the ocean. The late Devonian extinction eliminated 70% of species, reshaping marine ecosystems.  

Scientists have long suspected that damage to the ozone layer played a role in these ice ages. Now, researchers say supernovas could have been the trigger. Their findings, published in the Monthly Notices of the Royal Astronomical Society, show that the timing of nearby stellar explosions aligns with these mass extinctions.  

A supernova — the explosive death of a massive star — can leave behind a black hole or neutron star. These cosmic blasts are element factories, spreading carbon, calcium, and iron across space, fueling new generations of stars and planets. This is why astronomer Carl Sagan famously said we are made of "star stuff."  

Yet, supernovas can also be destroyers. If one explodes within about 65 light-years of Earth, its radiation could strip away the ozone layer, exposing the planet to harmful ultraviolet rays and acid rain.  

Using sky survey data, including from the European Space Agency's Gaia mission, the researchers analyzed nearly 25,000 massive stars within 3,260 light-years of the sun. They calculated that supernovas occur near enough to impact Earth roughly every 400 million years.  

Fortunately, the closest stars poised to explode — like Betelgeuse and Antares — are more than 500 light-years away. So, while these cosmic events shaped Earth's past, they are unlikely to bring another ice age anytime soon.