Cosmic Collisions

by Jonathan Knight / Illustrations by Utako Kikutani

What Happens When Galaxies Collide?

 Toomre and the first models. See the earliest computer simulations of colliding galaxies.

Images of a Collision. What does a collision between two galaxies look like?

Galactic encounters on the big screen. Computer simulations and IMAX.

Dark Matter. Will the universe collapse to a single point? Click here to find out how computer simulations have yielded clues to the answer.

Star Factories. Do starburst galaxies originate with galactic collisions?

Lyman alpha forest. How do galaxies form? Computers can simulate the evolution of galaxies from humble cosmic gas

 To a stargazer, the universe appears as placid and calm as a frozen lake. But in reality, it is a violent, churning cauldron in which galaxies explode into existence, then collide and rip each other apart, flinging debris across the cosmos. Astronomers would love to see this violence, but all they get are snapshots of galaxies in various stages of impact. To see collisions in motion, they would need a time-lapse camera that could compress a billion years into an hour.

Lars Hernquist, an astrophysicist at the University of California, Santa Cruz, has devised the next best thing: supercomputer simulations of cosmic encounters. Hernquist's computer models have helped astronomers understand the origin of starbursts, as well as estimate the quantity of dark matter that surrounds and molds galaxies. Recently, Hernquist has probed the evolution of disc galaxies like our own from their humble beginnings as diffuse interstellar gas. His models have changed the way astronomers think about the universe.


Images of a Collision

Galactic Encounters 

Dark Matter

 Star Factories

 Lyman-alpha Forest

 About the Authors

Related Sites

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