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A supernova, an explosive end to a star’s life cycle, has the potential to impact planets in its proximity, including Earth. If a star were to go supernova within close range of our planet, the radiation it emits could lead to catastrophic consequences for life as we know it. However, any significant threat would depend on the star’s distance and type. A supernova would need to be within approximately 25 to 30 light-years of Earth to disrupt the atmosphere to the point of causing severe ecological damage, particularly through the depletion of the ozone layer, which protects us from harmful ultraviolet (UV) radiation. Fortunately, no stars with imminent supernova potential exist within this distance from Earth.
Supernova Risks and Distance
Betelgeuse, located roughly 650 light-years away, is one of the most prominent supernova candidates, but its distance means it poses no real threat. If it explodes, it would produce a spectacular, but harmless, light display visible from Earth. According to Professor Paul Sutter, an astrophysicist, the closest potentially dangerous star is Spica, located 250 light-years from Earth, well beyond the range that would pose a significant risk to our planet’s biosphere.
Potential Effects of a Nearby Supernova
Should a star explode within the critical 30-light-year radius, the consequences would be severe. The radiation emitted, including X-rays, gamma rays, and cosmic rays, could disrupt molecular bonds in Earth’s atmosphere. This disruption would likely lead to the formation of nitrogen oxides, which are known to break down the ozone layer. With a weakened ozone layer, UV radiation from the Sun would be more intense, threatening the survival of photosynthetic organisms and potentially destabilising ecosystems.
The Threat of Gamma-Ray Bursts
While rare, gamma-ray bursts (GRBs) are also recognised for their destructive potential. Caused by hypernovae or neutron star mergers, these events release powerful beams of radiation that can reach across thousands of light-years. Although GRBs are harder to predict and less understood, they pose a greater risk due to their highly concentrated energy, which could threaten life on Earth even from a more significant distance.
Long-Term Outlook and Galactic Positioning
As the solar system moves through the Orion Arm of the Milky Way, astronomers suggest the likelihood of a nearby supernova could increase. Despite this, the odds of Earth experiencing such a close and dangerous supernova event remain low, estimated to occur only a few times every billion years. While unlikely, a supernova event in this range could alter Earth’s biosphere, as some scientists theorise occurred during a mass extinction event approximately 360 million years ago.