Many individuals are aware of the hypothesis that an **asteroid** impacted Earth approximately 66 million years ago, striking what is currently known as the Yucatán Peninsula and contributing to the extinction of numerous **dinosaurs**.
Nonetheless, this was not the sole mass extinction event throughout Earth’s timeline—it’s simply the most well-known. Researchers propose that there have been at least five mass extinction events over the last 500 million years, and not all were instigated by **space** debris. Two of these occurrences, one from 372 million years ago and the other from 445 million years ago, are believed to have been sparked by ice ages.
A recent investigation, grounded in a stellar survey of the **Milky Way**, indicates that these severe cooling phases might have been initiated by dying stars situated **light-years** away.
>”If a massive star were to explode as a supernova in proximity to Earth, the consequences for life on our planet would be catastrophic,” stated Nick Wright, an astrophysicist at Keele University in the UK. “This research implies that such an event could have already transpired.”
### The Role of Supernovas in Mass Extinctions
The origins of the **late Devonian** and Ordovician mass extinctions—taking place 372 and 445 million years ago, respectively—remain unclear. The Ordovician extinction is believed to have exterminated around 60% of invertebrate marine species during a period when most terrestrial life was oceanic. The late Devonian event was even more drastic, eliminating 70% of all species and drastically changing the variety of fish that survived.
Researchers have long theorized that these ice ages ensued after damage to the ozone layer of Earth. Current studies suggest that **supernovas**—massive stellar explosions—might have caused these atmospheric disturbances. The occurrence rates of nearby supernovas coincide with the times of both extinction events. Their **findings**, published in the *Monthly Notices of the Royal Astronomical Society*, lend credence to this hypothesis.
A **supernova** is a massive **stellar death** phenomenon that can result in the creation of a **black hole** or a **neutron star**. It represents the most powerful and brilliant type of explosion recorded in the **universe**.
These cosmic events act as factories for elements, according to **NASA**. They produce vital elements such as carbon—the building block of life on Earth—as well as calcium and iron, which compose bones and blood. These substances are then dispersed throughout space, aiding in the formation of new stars and planets.
This idea is what astronomer Carl Sagan alluded to when he claimed that humans are comprised of “star stuff.” The very elements constituting our bodies originated in the hearts of stars and were spread across the cosmos when those stars perished.
### Supernovas: Creators and Destroyers
While they contribute to the emergence of new life, supernovas can also pose significant threats.
>”Supernova explosions release heavy chemical elements into the interstellar medium, which subsequently serve to form new stars and planets,” articulated Alexis Quintana, the lead author of the study. “However, if a planet, including Earth, is situated too near such an explosion, the repercussions can be catastrophic.”
A nearby supernova could emit intense radiation that depletes Earth’s ozone layer. Scientists define “nearby” as approximately within 65 light-years. In the absence of the ozone layer, Earth would be vulnerable to dangerous ultraviolet radiation from the sun, as well as acid rain.
### How Likely Is Another Nearby Supernova?
To evaluate the probability of such an event, researchers examined data from extensive sky observations, including the European Space Agency’s **Gaia mission**. They performed a census of nearly 25,000 “OB stars”—hot, massive stars—within 1,000 parsecs (about 3,260 light-years) of the sun. These stars are at least twice as hot as the sun’s surface.
By analyzing these stars, scientists approximated the frequency of supernovas in our galactic vicinity and throughout the Milky Way. Their calculations indicate that a supernova occurs within a perilous range of Earth approximately once every 400 million years.
The closest stars that might explode within the next million years include Antares and **Betelgeuse**. However, both are over 500 light-years distant—sufficiently far that their explosions are unlikely to precipitate another ice age.
Thus, although supernovas have likely influenced mass extinctions in Earth’s history, the probability of one inciting a similar disaster in the foreseeable future remains minimal.