Supernova! It’s the largest explosion that takes place in space, but how do the deaths of giant stars in our own galaxy affect Earth and other planets?
What would happen if a supernova went off on in our corner of the Milky Way?
Does it matter? Absolutely. The massive amount of radiation emitted by a supernova explosion could lead to climate change on planets enveloped by it.
So whether a supernova has gone-off close by might be a critical question in piecing together the history not only for our planet, but also for potentially habitable planets in other star systems.
It’s also something of a live issue for our Solar System given the confusion over whether red supergiant star Betelgeuse—which we know will go supernova in the next 100,000 years—could explode rather sooner.
After all, Betelgeuse just got closer.
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The effects of a supernova going off are unknown, but there could be clues in the trees. New research published in the International Journal of Astrobiology suggests that supernova explosions occurring in the Milky Way—though still many thousands of light-years from Earth—may have left traces in our planet’s biology and geology.
In a few short months a supernova explosion can release as much energy as the Sun will during its entire lifetime.
When and where supernovae occurred is important. When a star explodes in a supernova explosion it emits radiation, and it’s thought that planets recently exposed to radiation from supernovae are less likely to be habitable.
So Robert Brakenridge, a geoscientist at the University of Colorado Boulder, compared known supernovae with tree ring records.
Supernovae can be seen by astronomers because they leave visible remnants, called nebulae.
Sure enough, the timing of supernovae that occurred relatively close to the Solar System in the last 40,000 years appear to coincide with spikes in radiocarbon levels seen in tree rings.
The atom in question in carbon-14, a carbon isotope that is formed when cosmic rays from space bombard Earth. A spike in levels could indicate that energy from a distant supernova has traveled hundreds of thousands of light-years to our planet.
After all, scientists have recorded supernovas in other galaxies that have produced a massive amount of gamma radiation.
“There’s generally a steady amount year after year,” said Brakenridge about levels of carbon-14. “Trees pick up carbon dioxide and some of that carbon will be radiocarbon,” he added.
Brakenridge found eight close supernovae that generally tally with spikes in the radiocarbon record on Earth, but four that are a really good match:
- Vela supernova: 12, 740 years ago, 815 light-years = 3% increase in radiocarbon on Earth.
- S165 supernova: 7,431 years ago, 2,300 light-years away = 2% increase in radiocarbon on Earth.
- Vela Jnr. supernova: 2,765 years ago, 650-700 light-years away = 1.4% increase in radiocarbon on Earth.
- HB9 supernova: 5,340 years ago, 1,000-4,000 light-years away = 0.9% increase in radiocarbon on Earth.
“Their ages, distances and expected gamma ray emissions are compatible with observed terrestrial effects that are also predicted from theory and modeling,” reads the paper.
It’s possible that these four supernovae could have led to four climatic changes on Earth.
However, none of the evidence unearthed is a “smoking gun.” The spikes in radiocarbon could be attributed to our own Sun. Solar flares and huge ejections of energy from the surface of the Sun are thought to be capable of producing similar spikes in radiocarbon on Earth, but that’s not proven.
So Brakenridge’s findings suggest that relatively close supernovas could theoretically have triggered specific disruptions to Earth’s climate. “We’re seeing terrestrial events that are begging for an explanation,” said Brakenridge. “I think the supernovae hypothesis has been dismissed too quickly,” he added. “These are extreme events, and their potential effects seem to match tree ring records.”
Wishing you clear skies and wide eyes.