Why are some black holes bigger than others? An astronomer explains how these celestial vacuums grow

Black holes are dense astronomical objects with gravity so strong that nothing, not even light, can escape.

Some smaller black holes are sprinkled randomly throughout galaxies like our Milky Way .

Other gigantic ones, called “supermassive” black holes, lie at the centers of galaxies.

Some scientists think supermassive black holes might form by many stars colliding and collapsing at once.