An artists conception of a quasar.
It’s hard to overstate the shock astronomers felt when the true nature of quasars began to dawn on them in the early 1960s. At first, these mysterious objects seemed like ordinary stars, tucked in the embrace of our familiar Milky Way. But a closer look revealed that they were billions of light-years away, far beyond the confines of our galaxy. To be visible at such vast distances, a quasar must, by itself, have been as bright as an entire galaxy, but somehow squeezed into a pinpoint of light and nobody knew how such a thing could be possible.
It took a while, but theorists finally agreed that quasars are really giant black holes that lurk in the cores of distant galaxies, sucking in surrounding gases and heating them until they shine halfway across the universe. Meanwhile, in the decades since those first, startling discoveries, scientists have boosted the number of known quasars from a tiny handful to some 200,000 across the sky.