What happens if a star explodes near Earth?

The answer is not simple and depends on the distance between the exploding star and our planet.

The phenomenon of exploding stars , also known as supernovae, has always been intriguing because of the powerful explosions, the brilliant light that can illuminate a corner of the universe. But are these giant explosions a real threat to Earth? The answer is not simple and depends on the distance between the exploding star and our planet.

Does it really "explode"?

In a broader sense, our Sun also 'explodes' regularly, especially during periods of high activity. Events like solar storms and coronal mass ejections are small explosions that release large amounts of charged particles and radiation. These events usually only cause radio interference, dislodge satellites, or create spectacular auroras. However, if a large solar storm were to directly impact Earth, it could cause serious damage to electrical and telecommunications systems. That's why scientists keep a close eye on the Sun's activity.

The Eta Carinae Nebula surrounds one of the largest stars in our Milky Way galaxy after an explosion in the 19th century.

But these 'explosions' are minor. Some stars much larger than the Sun can undergo supernova explosions – events that mark the end of a massive star. These are extremely violent astronomical events in which the star briefly shines brighter than the entire galaxy, releasing huge amounts of energy and radiation.

When does a supernova actually become a danger?

A supernova is only truly dangerous if it occurs close to Earth. 'Close' is generally defined as being within 30-50 light years. If a star explodes within this range, the intense radiation from the explosion can burn up the atmosphere, destroying the ozone layer and leaving Earth exposed to ultraviolet radiation from the Sun. This effect can last for thousands of years, with serious consequences for life.

In addition, high-speed protons and electrons from the explosion would continuously "attack " the Earth, increasing the risk of cancer in living things and causing unpredictable climate changes. If the explosion were closer, the intense heat and light could increase the Earth's temperature as if we had a "second Sun", leading to the collapse of global ecosystems.

The remains of the Kepler Supernova, the most recent known supernova in the galaxy. At a distance of 20,000 light years, there are no negative consequences for us.

What is a safe distance?

If a supernova occurs more than 200 light years away , its impact on Earth will be very small, almost negligible. This is because of the "inverse square" principle : the intensity of radiation decreases with the square of the distance. For example, a supernova 200 light years from Earth would be only 1/40th as dangerous as one 30 light years away.

Fortunately, the nearest star that could go supernova in the future is Betelgeuse, which is between 530 and 900 light years away from Earth – too far away to cause any serious damage. Still, it would be a beautiful sight, with the light from the explosion clearly visible to the naked eye, even during the day.

While supernovae at long distances are generally harmless, there are exceptions. Some supernovae emit large amounts of X-rays or gamma rays—radiation that is far more capable of destroying the ozone layer than chemicals like CFCs. If Earth were caught in the 'beam' of this radiation, even if it were hundreds of light-years away, the consequences would be dire.

In addition, rare explosions such as hypernovas or kilonovas – which are many times more powerful than regular supernovas – can pose a threat at greater distances. However, these phenomena are rare and usually occur in regions very far from Earth.