What Happens If Stars Collide?

Stars are some of the most impressive and gorgeous objects within the universe. From our vantage point, looking up at the cosmos from the earth, we can see more stars than we can count, but that’s not even a fraction of how many stars there are in the universe.

With so many stars, you may be wondering what would happen if two of them were to interact with one another. If two objects as big and bright as stars collided – what havoc would be caused? What would happen to all of the planets, moons, and asteroids that orbit them? Would anything be able to survive?

That’s why we’ve created this short exploration of the topic. We’ll be going through what happens when two stars collide, as well as some examples of what has happened in the universe when this has happened in the past. We’ve also included a handy FAQ section to help answer some of your burning questions – so if there are any of the more technical terms in this article you are unfamiliar with, check down below! 

What Is A Star?

Before we explain what would happen when two stars collide, first it’s important to give a brief overview of what exactly a star is. In its most common and well-known form, the word star refers to any gigantic, self-luminous body of gas that shines via radiation caused by its internal energy composition. 

The smallest stars we know of are named red dwarves,’ because they appear red and small. The reason for their size is that they burn small amounts of hydrogen in their cores and radiate small amounts of light. If we go up one category then we find stars such as our own sun, which has medium mass and brightness. One category up again and we’ll find giant stars which are much larger and brighter than our own sun. 

There are also other objects in the universe that share the name of ‘star,’ such as neutron stars and white dwarves, though these only occur at the end of a star’s lifecycle and are not stars in the same way as an object like our sun may be classified as. 

What Would Happen If Two Stars Collide?

First, it’s quite important to point out that it is very rare for two stars to collide. We only see instances of this occurring in the densest parts of galaxies, for example in the center where there are massive clusters of stars. The collision of two stars is called ‘stellar collision’ by scientists and often happens within clusters. 

There are different kinds of stellar collisions that we will now explore.

Neutron Star Merger

A neutron star merger happen when two white dwarf stars merge with one another. When two neutron stars orbit one other, over time they begin to get closer to one another. Eventually, they will meet and when this happens this merge creates either an even heavier neutron star (kind of like the two of them have added to one another) or a black hole.

Type La Supernova

When two white dwarfs form a binary system, they can sometimes cause large explosions which scientists have called ‘Type La Supernovae’. This is what is known as a supernova explosion when in a matter of moments, the white dwarf’s mass is rapidly thrown out into space. From a distance, supernovas are gorgeous to view, and some of the most beautiful pictures in space we have come from photographing such events. 

Thorne-Zytkow Objects 

Now, if a neutron star gets close enough to collide with a red giant that has a small mass and density, something quite strange can happen. In particular circumstances such as these, it is possible that both can live in the form of a hybrid star scientists call the Thorne-Zytkow object. This is essentially a neutron star that is surrounded by a red giant. 

An Alternative – Binary Star Systems

One of the main reasons that two stars colliding is rare, is because you are much more likely to see two stars becoming gravitationally bound. Scientists call this Binary star system – when two stars are bound and orbit one another. 

The History Of Stellar Collision

If you thought of the idea of two stars colliding yourself, then you went through some of the same thoughts as astronomers throughout history. The idea of stellar collision is not a new thing, but it wasn’t until the early 20th century that astronomers began to have the technology to be able to properly observe it.

With the invention and success of the Hubble Space Telescope in April 1990, scientists have been able to detect evidence of stars colliding within globular clusters of stars that occur most often in the densest parts of galaxies. 

Final Thoughts

We hope that this article has taken you through some of the possibilities that can occur when two stars collide. Though scientists are quite sure that this phenomenon occurs, it is worth noting that much evidence is still being collected and there are likely far more eventualities than what we know at the moment.

Because of some of the more technical language used in this article, we’ve included a short FAQ down below to take you through the more challenging terms used so far. 


What Is A White Dwarf?

A white dwarf is a type of star, usually classified by its small size. White dwarves can be the size of a planet, which is far smaller than what a regular star is. White dwarves are created when a low-mass star burns out all of its internal nuclear fuel and begins to lose its outer layers. 

White dwarves are sometimes called ‘dead stars’ because although they still have some brightness, they are no longer constantly burning the same internal fuel that other stars like our sun are. 

What Is A Globular Cluster?

A globular cluster of stars is a large grouping of old stars (such as white dwarves) that have been grouped in a spherical formation. They are called globular because of their spherical form and are some of the largest groupings of stars we have observed in the universe. 

What Is A Neutron Star?

A neutron star is the collapsed core of a giant star. Neutron stars are typical of very small radius and very high density. They are created with lots of closely packed neutrons. Though why exactly neutron stars exist is unknown, they are believed to have formed by the gravitational collapse of a massive star after a supernova explosion. The alternative seems to be that the star would instead become a black hole. 

What Is A Black Hole?

A black hole is an area of space-time where gravity is so strong that nothing, not even light, can escape it. Black holes are one of the biggest mysteries within astrophysics and though there are many theories as to what happens beyond their event horizon (the point from which nothing can escape) we do not yet fully understand them. 

Gordon Watts