The study implicates supernovae in both the late Devonian and Ordovician extinction events, which occurred approximately 372 million and 445 million years ago, respectively. The Ordovician event led to the demise of 60% of marine invertebrates when life was primarily oceanic, while the late Devonian event eradicated nearly 70% of all species, profoundly altering aquatic ecosystems.
Although past research linked these extinctions to ozone layer depletion, no definitive cause had been identified. The new findings, published in *Monthly Notices of the Royal Astronomical Society*, reveal that the timing of nearby supernovae aligns with these extinction events, strengthening the hypothesis that cosmic explosions played a role.
"Supernova explosions bring heavy chemical elements into the interstellar medium, which are then used to form new stars and planets," explained lead author Dr. Alexis Quintana, formerly of Keele University and now at the University of Alicante. "But if a planet, including the Earth, is located too close to this kind of event, this can have devastating effects."
Dr. Nick Wright of Keele University emphasized the destructive potential: "Supernova explosions are some of the most energetic explosions in the universe. If a massive star were to explode as a supernova close to the Earth, the results would be devastating for life on Earth. This research suggests that this may have already happened."
The team reached their conclusion by conducting a detailed survey of massive stars within a kiloparsec (about 3,260 light-years) of the Sun. Their analysis focused on the distribution of OB stars-hot, short-lived massive stars-using the Milky Way as a reference for stellar evolution and cluster formation.
By calculating the frequency of supernovae in the galaxy, the researchers gained insights into supernova remnants and the formation of black holes and neutron stars. Their data also have implications for future gravitational wave detection, a key tool in understanding the structure and origins of the universe.
The study included calculations of supernova rates within 20 parsecs (about 65 light-years) of the Sun, which were then compared to past mass extinction rates. These findings support the idea that supernovae were responsible for the late Devonian and Ordovician extinctions-two of Earth's five major mass extinction events-excluding those linked to asteroid impacts or ice ages.
"We calculated the supernova rate close to Earth and found it to be consistent with the rate of mass extinction events on our planet that have been linked to external forces such as supernovae," Dr. Wright stated.
While supernovae occur in galaxies like the Milky Way at a rate of one or two per century, astronomers note that only two nearby stars-Antares and Betelgeuse-pose potential supernova threats within the next million years. However, both are more than 500 light-years away, and simulations suggest an explosion at such a distance would likely have minimal impact on Earth.
Research Report:An optically led search for kilonovae to z~0.3 with the Kilonova and Transients Programme (KNTraP)
Related Links
Royal Astronomical Society
Explore The Early Earth at TerraDaily.com
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