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Galaxy Collision

Multi-particle gravitational simulation of merging galaxies

Particles

Two galaxies approach each other head-on. Their mutual gravity tears out tidal tails and bridges before they merge into a single elliptical remnant.

Galaxies

Presets

Playback

Display

Center On

Controls

Space Play / Pause
R Reset simulation
Drag to pan view
Scroll to zoom
Center On → follow a galaxy

Tips

Head-On — low speed → slow merger with strong tidal features; high speed → fast fly-through
Tidal — impact parameter + disk tilt shape the tidal tails and bridges
Minor — satellite gets stripped into long stellar streams
Dark matter halo toggle shows the extended mass distribution

Units

Distance: kpc (kiloparsecs)
Time: Myr (megayears)
Mass: 1010 M☉
E 0.000 t 0 Myr d 0.0 kpc ΔE 0.000%
How to Use

Head-On: Two galaxies collide directly. Adjust masses and approach speed to see how the encounter changes. Higher speed produces a fast fly-through; lower speed leads to a slow, dramatic merger with strong tidal features.

Tidal Encounter: A glancing fly-by with an impact parameter (offset). This produces the spectacular tidal tails and bridges seen in real interacting galaxy pairs like the Antennae (NGC 4038/4039). Disk inclination angles strongly affect the shape of the tails.

Minor Merger: A small satellite galaxy falls into a much larger host. Tidal forces strip stars from the satellite into long streams, similar to the Sagittarius dwarf galaxy being absorbed by the Milky Way.

Physics: Each galaxy core interacts gravitationally with the other core and with all star particles. Star particles respond only to the two massive cores (restricted N-body), enabling smooth simulation of hundreds of particles. Integration uses the symplectic leapfrog (velocity Verlet) method.

Controls: Space to play/pause, R to reset, mouse wheel to zoom, drag to pan. Units: distances in kiloparsecs (kpc), time in megayears (Myr), mass in 1010 solar masses.