Scientists at Keele University have said there is a strong possibility that mass extinction events throughout the history of life on Earth could have been caused by the effects of nearby supernova explosions in the Milky Way. 

The findings have been published in the Monthly Notices of the Royal Astronomical Society journal, after the researchers conducted a “census” of massive stars within a kiloparsec (around 3,260 light-years) of the Sun. 

The research team were studying the distribution of these massive stars, known as OB stars, to learn more about how star clusters and galaxies form using the Milky Way itself as a benchmark, and the rate at which these stars form in our galaxy. 

This census allowed the researchers to calculate the rate at which supernovae occur within the Galaxy, which is important for observations of supernovae, and the production of supernova remnants and massive stellar remnants such as black holes and neutron stars throughout the universe. The data will also be useful for future development of gravitational wave detectors, which are a useful tool for scientists studying the structure and origins of the universe.  

As part of this they calculated the supernova rate within 20 parsecs of the Sun, or approximately 65 light-years, and compared this with the approximate rate of mass extinction events on Earth that have previously been attributed to nearby supernovae. This excludes extinction events linked to other factors like asteroid impacts or the ice ages. 

Comparing these data sets, the researchers found that the two rates showed a good agreement, which supports the notion that a supernova explosion could have been responsible for those extinction events whose causes are not fully known, such as the late Devonian and late Ordovician extinction events, which respectively occurred 372 and 445 million years ago. A nearby supernova explosion could strip the Earth’s atmosphere of its ozone, exposing surface-dwelling life to harmful ultraviolet radiation.  

Lead author Dr Alexis Quintana, formerly from Keele University and now at the University of Alicante, said: “It is a great illustration for how massive stars can act as both creators and destructors of life. Supernova explosions bring heavy chemical elements into the interstellar medium, which are then used to form new stars and planets. But if a planet, including the Earth, is located too close from this kind of events, this can have devastating effects.” 

Dr Nick Wright, from Keele University, added: “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.”

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