Can A Supernova Destroy A Galaxy?

Supernova explosions are some of the most impressive celestial phenomena that we have ever witnessed from our place in the Universe.

Through a telescope, Supernova look like gorgeous explosions of light across stars, among the prettiest and most colorful things an astronomer can go looking for. 

Upon learning that a Supernova is the massive explosive remnants of a star, you might wonder the knock-on effects of what that kind of power does to space around them. For example, if a star exploded into a supernova, what would happen to the galaxy around it? Could there be a Supernova large enough to destroy an entire galaxy?

 If you’ve ever found yourself wondering about this – then this is the article for you to read! We’ve written an in-depth discussion of Supernovas: what they are, what they do, and the effect they have on the wider known universe. We’ve also added a short FAQ section to explain some of the more technical terms used in the article. 

What Exactly Is A Supernova?

Before we outline some of the catastrophic effects that supernovas can have in the wider universe, let’s first make sure we know exactly what one is and where they come from. In short – a supernova is the greatest explosion in the known universe. Nuclear blasts don’t even come close to the sheer magnitude of a supernova explosion. There are different causes for supernovas but the most common happen as a result of a star dying.

In life, massive stars burn large amounts of nuclear fuel in their center which in turn produces a lot of energy. The center of a star is astronomically hot, which means a lot of pressure. The pressure pushing outwards from the core, along with gravity pushing inwards are the two forces that keep a star together. However, this same process is what eventually will cause a large star to explode. 

Once it begins to deplete all of its nuclear fuel, the inside pressure begins to drop off. This means that the external force of gravity pushes the star inwards into a collapse. The entire mass of the star collapses in a matter of seconds and this causes the star to explode.

The supernova explosion leaves behind a few things, including nebula which are giant interstellar clouds of helium, dust, and hydrogen. This nebula can remain after the initial explosion and are called ‘supernova remnants.’ The rest of the star is then likely to become either a neutron star or a black hole. 

The other kind of supernova that we know of is when a white dwarf – a dead, weakly burning star – collides with another star. When this happens the densely packed white dwarf can explode into a supernova. It’s worth noting that this second option is the less common occurrence in the observable universe. 

Has A Supernova Ever Destroyed A Galaxy? 

Now we know about the impressive magnitude of supernova explosions, we can begin to explore their impact on the universe around them. The question is whether or not a Supernova could be large enough to destroy a galaxy.

Astronomers believe that solar systems 50 light-years away from a supernova would likely be safe, though this is an estimate. Remember – light years is a measure of distance, not time. It is how far light can travel in a year. 50 light-years is a long way – but it is nothing when compared to the size of our galaxy, the Milky Way.

The Milky Way is 100,000 light-years away. With this in mind, it seems very unlikely that a supernova explosion would be able to destroy a galaxy. We have no known instances of this happening. That’s not to say that a supernova isn’t massively damaging to everything around it. For example, if our solar system was within 50 light-years of an exploding star, we would likely be wiped out.

But that said, the size a supernova would have to be to destroy an entire galaxy is beyond what we have observed in the universe. 

Hypernova

There is, however a kind of Supernova Explosion known as a Hypernova. It’s a word scientists have chosen to describe an extremely volatile and large supernova explosion. They occur during the collapse of an extreme core star.

This would have to be a massive star that collapses in on itself to form a rotating black hole. We haven’t been able to observe many hypernovas, but the first was detected in the ESO 184-G82 spiral galaxy. Scientists aren’t certain that this was indeed one, but an intense gamma-ray burst has raised suspicions.  

Thankfully we don’t have to worry about such a large supernova in our galaxy right now, because this one is around 140 million light-years away. 

Supernova In The Milky Way Galaxy

So how far away are we from a supernova? It’s worth noting that supernovas in our galaxy occur once around every 50 years. They are rare events, but considering the vast number of stars in our galaxy (100 thousand million) it’s not really surprising we only detect them infrequently. Even though one may occur every 50 years, we haven’t detected one since 1604. 

This supernova was observed on the 9th of October when several people noticed the appearance of a new star in the sky. Johannes Kepler is the most notable astronomer who studied this new star – and the remnants of this supernova we can still see in the night sky is now known as Kepler’s Supernova.

Of course, at this time in human history astronomers had no understanding of the life cycle of stars and supernovas, but it was studied to the best of their abilities.

Today, Kepler’s supernova is one of the most observed in history and it has helped to prove and further our understanding of this interstellar phenomenon. After scientists invented the modern naming system for supernovae, it was called SN 1604, though many people still refer to it as Kepler’s Supernova or Kepler’s star. 

Final Thoughts

We hope that this article has shed a giant ray of light on the gorgeous interstellar phenomena known as supernovas. Whilst they are the largest explosions we know of in the universe, they still come nowhere near to the size of a galaxy, which makes them unlikely to destroy an entire galaxy.

Still, we are certainly lucky not to be close to one – and perhaps in far future scenarios humanity will one day have to contend with an exploding star.

Until then, let’s be thankful we live in a relatively safe part of the universe and that we can continue to explore space and physics in peace! Below is a short FAQ to explore some of the more technical terms we’ve used in this article.

FAQ

What Is A Light-Year? 

A light-year is deceptively named because it is not a measure of time. It is a measure of distance. It is a way of describing how far light travels in a year. The official equation to explain this is 9.4607 × 1012 km which is approximately 6 million, million miles. When we try to measure the vast distances of space, numbers become difficult to imagine! 

What Is A Galaxy? 

A galaxy is a collection of different bodies in the universe, namely dust, gases stars, and their planets. The size of galaxies is difficult to imagine, with our Galaxy – The Milky Way – being 52,850 light-years. Galaxies are held together by gravity, a force that pulls objects towards each other.