Most of you have heard of a quasar but may not know what they are. Quasar is abbreviated from QUAsi StellAr Radio source- now referred to in astronomic material as QSO's, Quasi-Stellar Objects since it's been found that not all are radio emitters. Stellar refers to the fact that they look like stars to Earth telescopes, even Hubble.
3c273 in Virgo is the brightest quasar you can see in a backyard telescope. If it were ten parsecs away, as far as Pollux, it'd be almost as bright as our Sun! Our Sun at that distance would be fainter than Pollux!
It has an enormous "red shift" of its light spectrum, which tells us it's very very very fucking far away, so far the galaxy it's in can't be seen with the biggest telescopes on earth.
Quasars were a mystery in the sixties: a proper mechanism for how a relatively small, apparently stellar object could emit so much energy had yet to be proposed.
Long story shortened, it's now recognized that they're Active Galactic Nuclei, probably a common occurrence in the early history of most Spiral galaxies: infalling gas and dust are incipient on the galactic central hub, and a great deal of energy is emitted along the axis in the form of a nuclear condensation or "jet" of great light intensity.