How might two colliding spiral galaxies tend to create an elliptical galaxy?

Question

Answer

The collision creates a larger galaxy and elliptical galaxies are always larger

Answer

The gas in the disks of the galaxies is expelled into intergalactic space by gravitational interactions

Answer

The orbits of the stars get randomised during the collision, while their gas disks collide and form stars

Answer

The heat created by collisions between stars causes the disks to puff out into a spherical shape

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