Near-Earth supernova

A near-Earth supernova is an explosion that happens when a star dies and occurs close enough to the Earth, within about 33 to 978 light-years. Because it happens so close, such an explosion can have important effects on life and the environment here on our planet. These explosions are powerful events that mark the end of a star’s life cycle.

Scientists believe that around 20 supernova explosions have happened within 300 parsecs (about 978 light-years) of the Earth in the last 11 million years. These explosions often occur in areas where new stars are being born, known as active star-forming regions. Currently, there are about 12 stars that are considered possible candidates for becoming near-Earth supernovas in the future.

Studying these events helps us understand how stars live and die, and how such cosmic explosions might influence our own solar system. For more information about how humans have observed these explosions throughout history, see the History of supernova observation.

Effects on Earth

On average, a supernova explosion happens close enough to Earth to have effects roughly every 240 million years. The main danger comes from gamma rays, a type of high-energy light. These rays can break down molecules in Earth’s upper atmosphere, especially oxygen and nitrogen, creating substances that wear away the ozone layer. This layer normally protects Earth from harmful solar and cosmic radiation. Without it, more harmful light would reach the surface, which could hurt plants and animals, especially in the oceans.

In the past, explosions from nearby stars might have changed Earth’s climate and helped increase the variety of life. These events sent more cosmic rays toward Earth, leading to cooler temperatures and stronger winds. This mixing brought more nutrients to shallow ocean waters, supporting more life. One famous star, Betelgeuse, might explode in the future, but it would likely take millions of years to happen.

Risk by supernova type

A nearby supernova, which is an explosion from a dying star, could affect Earth if it happens close enough. Large stars that might explode in the next 1,000 years are within a few hundred light years of us, but they likely won’t harm Earth much even if they explode.

If a Type II supernova happens within about 26 light-years, it could damage Earth’s ozone layer. Scientists study how radiation from past supernovae, like SN 1987A in the Large Magellanic Cloud, might affect our planet. Type Ia supernovae, which come from small, dim stars, could be more dangerous if they happen very close to Earth, but we don’t know when or where they will occur.

Past events

A nearby supernova helped shape the Solar System about 4.5 billion years ago and may have even helped form it. Over time, supernovae have created the heavy elements needed for life on Earth.

Scientists have found signs of past supernovae in rocks on Earth, including a special type of iron called iron-60 in deep-sea rocks of the Pacific Ocean. This suggests a supernova happened relatively close to our solar system in the last few million years.

Some researchers think supernovae could have caused mass extinctions in Earth’s past, like the one that happened near the end of the Ordovician period. In 1998, a supernova remnant called RX J0852.0−4622 was discovered, possibly exploding around the year 1200. If it was as close as some scientists believe—about 650 to 700 light-years—it would be a rare event.