This is the Vela supernova remnant in the Southern Hemisphere constellation Vela. Some 13,000 years ago, a star exploded as a supernova, leaving behind its dusty remains in the nebula we see here. A new study examined the Vela supernova remnant and others, looking for a link between supernovas and past climate shifts on Earth. Image via CTIO/ NOIRLab/DOE /NSF /AURA. Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani & D. de Martin (NSF NOIRLab).
Supernovas might be linked to past climate shifts
Massive stars end their lives in powerful supernova explosions, ejecting high-energy radiation across the galaxy. A galaxy like our Milky Way should have a supernova explosion about every 50 years. The Milky Way spans 100,000 light-years, and studies have shown that for a supernova to impact Earth, it would have to be about 100 light-years away. But a new study from the University of Colorado Boulder said on June 10, 2025, that much more distant supernovas might have changed Earth’s climate in the past.
Robert Brakenridge of the University of Colorado Boulder is the author of the new study. He looked at the past 15,000 years of Earth’s history. Specifically, he looked at abrupt climate changes over this time period. Then he looked for supernova remnants whose ages aligned with these climate change events. He wanted to know if the climate changes of the past could be linked to supernovas. Brakenridge said:
"We have abrupt environmental changes in Earth’s history. That’s solid, we see these changes. So, what caused them?"
Understanding if there’s a connection between supernovas and climate change could help people prepare for future supernovas that could also impact Earth’s climate. Brakenridge said:
"When nearby supernovae occur in the future, the radiation could have a pretty dramatic effect on human society. We have to find out if indeed they caused environmental changes in the past."
Brakenridge published his peer-reviewed paper in the June 4, 2025, issue of Monthly Notices of the Royal Astronomical Society.
Modeling supernova radiation
Brakenridge created a model of supernova radiation based on data from space telescopes. His model showed the kind of impacts Earth would face if this radiation collided with our atmosphere.
High-energy photons from a supernova smashing into Earth’s atmosphere would have two harmful effects on a part of Earth’s atmosphere called the stratosphere, which is the upper regions of where airplanes can fly. One of the results would be the thinning of a part of the stratosphere known as the ozone layer. The ozone layer protects life from the harmful radiation from the sun, or, in this case, a supernova as well. In addition, the supernova radiation would break down methane in the stratosphere. Methane is a powerful greenhouse gas.
So supernova radiation would lessen the protective force of the ozone layer while simultaneously weakening the greenhouse effect. Brakenridge said these effects could result in some animal extinctions, more wildfires and global cooling.
Examining tree rings
To understand what was happening with Earth’s climate in the recent past, Brakenridge looked at tree rings. Scientists measure the amount of carbon-14 in tree rings to look for influxes of radiation.
What is carbon-14? It’s a type of radioactive carbon that forms continually in the atmosphere. Cosmic ray particles interact with nitrogen in the upper atmosphere to create carbon-14. Eventually, carbon-14 combines with oxygen to form carbon dioxide. Over a few months, that carbon dioxide containing carbon-14 makes its way to the lower atmosphere. There, trees take it up and store it in wood tissue.
So Brakenridge looked at tree ring records spanning 15,000 years. What he found was 11 spikes of carbon-14 in the tree rings. He said these spikes might be the result of 11 corresponding supernovae. Brakenridge explained:
"The events that we know of, here on earth, are at the right time and the right intensity."
Examples of supernovas and climate dips
According to Brakenridge’s paper, the Vela supernova exploded some 13,000 years ago from a distance of 900 light-years to Earth. There was a corresponding abrupt cooling period on Earth starting 12,760 years ago that we know of as the Younger Dryas.
Brakenridge also pointed to the Hoinga supernova. This X-ray bright source is about 90 times the size of the full moon. It exploded some 15,000 years ago at a distance of 1,140 light-years from Earth. Brakenridge said it might be responsible for a carbon-14 spike 14,320 years ago and a cold period during the Older Dryas.
Brakenridge lists six other dates with carbon-14 spikes for which he also has plausible supernova candidates of appropriate distances and ages. Yet he says this is still just one possible explanation for these phenomena. Solar flares (rapid releases of energy from our sun) are still a possibility.
The Hoinga supernova remnant is about the size of 90 full moons, making it the largest supernova ever discovered in X-rays. It might be responsible for a cooling period on Earth more than 14,000 years ago. Image via eROSITA/ MPE (X-ray), CHIPASS/ SPASS/ N. Hurley-Walker, ICRAR-Curtin (radio).
Bottom line: A new study found that supernovas might be responsible for cooling periods on Earth. The onslaught of radiation could have affected our atmosphere, lessening the greenhouse effect.
Late Quaternary supernovae in Earth history – Monthly Notices of the Royal Astronomical Society