Dark matter binds galaxies together
And there's so much dark matter that its gravitational force is enough to hold entire galaxies – like our own Milky Way – together.
What force binds a galaxy together?
Most galaxies are not alone in the vast expanse of space, but are connected to one or more other galaxies by gravity. The same force that holds you onto the Earth can keep many individual galaxies bound together.
How are galaxies held together?
Galaxies are sprawling systems of dust, gas, dark matter, and anywhere from a million to a trillion stars that are held together by gravity. Nearly all large galaxies are thought to also contain supermassive black holes at their centers.
