Most large galaxies seem to have so-called supermassive black holes at their centers, containing millions to billions of times the Sun’s mass. The galaxy M87, for example, harbors a black hole weighing some 3 billion solar masses.
Yet even supermassive black holes don’t have enough “pull” to consume a galaxy. Their strongest influence reaches only to around 10 light-years, whereas most galaxies extend at least 1,000 times that scale. — Eliot Quataert, Theoretical Astrophysics Center, University of California at Berkeley