Toomre and the first models

aIn the early 1970s, Alar Toomre set a collision in motion with the first computer model of a agalactic encounter. Limited computing power kept the number of stars to 1,000 (real galaxies ahave hundreds of billions). Toomre assigned each star a mass and sent the two digital agalaxies hurtling toward each other.

aThe long streaks of stars called "tidal tails" that gravity spun off Toomre's galaxies matched athe features of collisions seen by telescope. But Toomre's models were too crude to probe aother complexities of galactic encounters such as what happens to the interstellar gas and ahow might dark matter affect the impact. These questions had to await the vast anumber-crunching power of supercomputers, still a decade away.