30 years ago, astronomers started playing around with making simulations of colliding galaxies. Computers were slow, so they could only keep track of a few hundred or thousand stars, which limited the models severely. The software had to keep track of every star, its location, velocity, and mass… the number of calculations is forbidding.
Things have come a long way. Now astronomers can track millions of stars using hydrodynamics codes, and then graphically display them giving them color, adding in dust, the effects of cloud collisions, supernovae… and the results are stunning.
This is something very much like what will happen between the Milky Way and Andromeda galaxies in about five billion years.
(Note the elapsed time of the animation: three billion years.)
