Answer: Supermassive Black Holes

In the early 1970s, Donald Lynden-Bell and Martin Rees hypothesized that the center of the Milky Way Galaxy was actually a supermassive black hole with a mass millions of times greater than our sun. It didn’t take long for observations to prove them right, by 1974 there was substantial evidence that a supermassive black hole was in fact the celestial anchor of the Milky Way.

Further research since then has firmly established that supermassive black holes are most likely at the center of nearly every galaxy in the observable universe, many with masses on an order of a trillion times greater than our sun.