Emmanuel Momjian

In the dense Virgo galaxy cluster, astronomers have spotted six strange clouds of neutral hydrogen — gas that emits no light and is therefore invisible to ordinary telescopes. Radio telescopes can pick it up, but where it came from was unclear.

In the first few hundred million years after the Big Bang, the universe was a dark ocean in which the first stars and black holes ignited. Some of those black holes shot out narrow jets of plasma traveling at nearly the speed of light. If such a jet points straight at Earth, we see it as a bright spot: a blazar.