New scientific research indicates that the violent death of massive stars—events known as supernovas—may have had significant effects on Earth’s climate over the course of its ancient history. A supernova occurs when a massive star exhausts its nuclear fuel and collapses under its own gravity, resulting in an explosion that sends vast amounts of energy and high-speed particles through space. Depending on the distance from Earth, a supernova can have devastating or more subtle atmospheric consequences. Scientists estimate that an event within 30 light-years would likely strip away Earth’s atmosphere, ending all life. However, even explosions occurring hundreds of light-years away could influence our planet’s environment, including its climate and biosphere.
Robert Brakenridge, a researcher at the Institute of Arctic and Alpine Research, has examined this possibility by linking astrophysical theories with physical evidence from Earth. Instead of focusing solely on the physics of supernovas, Brakenridge studied how radiation from these events might have actually interacted with Earth’s atmosphere. Using observational data from powerful space telescopes, he created a new model that shows how a burst of high-energy photons from a supernova could break down the ozone layer—Earth’s protective shield against harmful ultraviolet radiation from the Sun.
The loss of ozone would allow more solar UV rays to reach the planet’s surface, posing a danger to living organisms. Furthermore, ultraviolet light would also degrade methane in the stratosphere. Methane is a powerful greenhouse gas that helps trap heat in the atmosphere, so its reduction would weaken the greenhouse effect and lead to cooling on a global scale. This combination of ozone loss and declining methane could result in increased ultraviolet exposure, lower temperatures, heightened wildfire risk, and even mass extinctions.
To test whether such events have happened before, Brakenridge turned to Earth’s natural record keepers: trees. Tree rings preserve atmospheric carbon over time, including radioactive carbon isotopes like carbon-14 that spike during periods of intense cosmic radiation. By analyzing tree rings spanning the past 15,000 years, Brakenridge identified 11 distinct spikes in radioactive carbon that could coincide with ancient supernovas. Though promising, these findings remain inconclusive because solar flares from the Sun can also cause similar spikes. Cross-referencing tree ring data with evidence from ice cores and ocean sediments could help confirm or rule out supernova activity as the cause.
If verified, this connection would not only enhance our understanding of climate anomalies in Earth’s past but also help scientists predict and prepare for similar future events. One potential future threat is the star Betelgeuse, located about 700 light-years away, which is expected to go supernova within the next 100,000 years. Although not close enough to pose an extinction-level risk, the event could still disrupt Earth’s atmosphere and climate.
Brakenridge believes that with more sophisticated models and deeper astronomical observation, researchers can better understand how cosmic events like supernovas have shaped—and may continue to influence—life on Earth. This emerging field offers insight into the interconnectedness of stellar and planetary evolution.