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Galaxy Collider simulation

Interactive 3D galaxy collision simulation. Collide two spiral galaxies, tune mass, tilt and spin, and watch tidal tails, bridges and a final merger unfold over billions of years. Share your collision with a link.

What you’re looking at

Galaxy Collider recreates the classic Toomre & Toomre (1972) experiment: each galaxy is a massive core surrounded by a disk of stars, and the two cores fall toward each other. Stars feel both cores, so during a close pass they are flung into long tidal tails and bridges like those seen in the Antennae and Mice galaxies. An approximate dynamical-friction term drains orbital energy so the cores eventually merge into one galaxy — a likely, though not certain, fate for the Milky Way and Andromeda over the next several billion years.

How to use it

  1. Pick a preset — Milky Way + Andromeda, the Antennae, the Mice, a minor flyby or a retrograde collision — or set your own mass ratio, closest approach and disk tilts.
  2. Press play and drag to orbit the camera; scroll or pinch to zoom. Scrub the timeline to rewind.
  3. Flip a galaxy to spin backwards (retrograde) and compare how much weaker its tidal tails are.
  4. Press Share to copy a link that recreates your exact collision.

Questions

Will the Milky Way collide with Andromeda?

Andromeda is approaching at about 110 km/s. Current estimates give roughly even odds of a merger within the next 5–10 billion years. Stars almost never hit each other; the galaxies' shapes are rearranged by gravity.

What causes tidal tails?

During a close pass, stars on the near side of a disk are pulled harder than the core and stars on the far side are pulled less. That stretch flings stars out into long, curved tails. Disks spinning in the same direction as the encounter (prograde) form the strongest tails.

How accurate is this simulation?

It follows the Toomre & Toomre approach: stars are test particles moving under the gravity of two cores, which is enough to reproduce tails and bridges. Full research simulations also model dark matter halos, gas and star formation.