What happens when two galaxies collide? Although such a collision may continue for more than a billion years, these enormous encounters are quite common in the universe. Because most of the space inside galaxies is empty, however, the probability that stars from the two galaxies will collide directly with one another is very small. [source]
What actually subjects one or both galaxies to extensive changes—or may even lead to the destruction of one of them—is the gravity of the galaxies themselves. The interaction can ultimately cause the two galaxies to merge and form a larger galaxy. [source]
During a collision, the gas and dust clouds of the two galaxies encounter one another and trigger a wave of newborn stars, which continue to evolve even during the interaction between the galaxies. [source]
The animation below presents a computer simulation of the collision of two large spiral galaxies. Among the simulated moving images, actual observations made by the Hubble Space Telescope are also shown for comparison. [source] [source]
Our own galaxy, the Milky Way, has absorbed several smaller galaxies over its lifetime, and it is predicted that in several billion years it will merge with our larger neighbour, the Andromeda Galaxy. [source] [source] [source] [source] [source] [source] [source]
Animation: Frank Summers, Space Telescope Science Institute
Computer simulation: Chris Mihos, Case Western Reserve University, and Lars Hernquist, Harvard University [source] [source] [source]