How do galaxies collide without most stars crashing into each other?
Quick Answer
Because stars are so far apart, direct collisions are rare. The galaxies’ gas, dust, and gravity interact strongly and can reshape both galaxies over millions of years.
The Full Story
Galaxies are mostly empty space, so even when two of them merge, individual stars usually pass by without hitting anything. The dramatic effects come from gravity, which distorts the galaxies, and from gas clouds, which can collide and trigger bursts of star formation. The Milky Way is expected to merge with the Andromeda galaxy in about 4.5 billion years. Long before then, the two galaxies will already be gravitationally deforming each other.
Key Facts
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