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Stellar Collisions are the coming together of two astronomical bodies, which through the force of gravity, merge into one larger unit. In a more basic sense, a stellar collision is a collision of stars. It is predicted that over several hundred can take place somewhere in our galaxy, and astronomers also predict that this event occurs once every 10,000 years in our own milky way galaxy. . Also it is predicted, if the conditions are correct, that even three or four stars can collide and merge to make one star. While much is unknown about this theory, there are new strides being made every day in order to try to prove that this phenomenon occurs in the universe. Scientist have not been able to physically see the collision due to technological delays, but they are able to detect the gravitational waves created by these collisions which allows them to make predictions about what really occurs.

Astronomical Bodies Involved
Any star in the universe can be involved in a stellar collision; whether, it is alive, meaning fusion is still active in the star, or dead, fusion no longer takes place. Examples would include White Dwarf stars, Neutron Stars, Black holes, Main Sequence Stars, Giant stars, and Supergiants. Differerent types, masses, temperatures, and radius will result in different collisions or mergers. All bodies have different reactions in the way they collide due to forces such as gravity, and also due to the physical aspects of the star.

Type Ia Supernova
White Dwarfs are the remnants of low mass stars, and if a binary system with another star it can cause a large explosion known as type 1a Supernovae. When a white dwarf comes near a "live star", they come locked in by each other's gravity and begin a slow revolution around each other. While this happens the white dwarf is rotating and begins sucking gas from its companion star until it reaches the Chandrasekhar limit, in which carbon fusion begins in the core increasing the interior temperature. Since the white dwarf is made of degenerate matter there is no safe relation between pressure and temperature, because of this the reactions spreads outward at a runaway speed with no barrier to stop it.This causes a collapse of outside layers causing a supernova shockwave, and in a matter of seconds all of the white dwarfs mass is thrown into space.

Neutron Star Collisions
Neutron star collisions happen much like Type 1a supernovas. When two neutron stars travelling through the galaxy get caught inside each other's gravity they begin to revolve around each other becoming closer as time passes. Once these two neutron stars meet in the middle, a huge collision occurs. This creates a magnetic field that is trillions times stronger than that of earths, in a matter of one or two milliseconds. Also astronomer believe this event is what creates gamma ray bursts.

Discovery
While the theory of stellar collision has been around for a few generations of astronomers, the development of new technology has made it possible for it to be proven. The theory of Stellar Collisions started in 1764 when a cluster of stars known as Messier 30, was discovered by an astronomer known as Charles Messier. After years of observation, fellow astronomers came to the conclusion that the cluster was approximately 13 billion years old. . Around 250 years later after the launch of Hubble Telescope, astronomers where able to looks at individual stars instead of clusters as a whole. With this new technology they discovered that some stars, known as “blue stragglers” where younger than other stars in the cluster. Astronomers than hypothesized that stars may have “collided”, or “merged”, giving them more fuel so they continued fusion while fellow stars around them started going out.

Stellar Collisions and our Solar System
While stellar collision can be a very numerous in certain parts of the galaxy, the likely hood of one effecting our star directly is very small. A calculated prediction says the odd of our sun being in a stellar collision is 1 in 10 trillion, trillion years. . Even though our star will not be directly affected by this event, our earth can very easily be. Astronomers say that if a stellar collision happens within 100 light years of our earth is could destroy us. This is very unlikely though because there is no stellar clusters near our solar system.