How do black holes power quasars?
Quasars are the ultra-bright cores of distant active galaxies. Gluttonous supermassive black holes spew out energetic jets of particles and radiation, visible over billions of light-years.
Quasi-stellar radio sources, or quasars for short, are the ultra-luminous cores of very distant galaxies, blowing opposing jets of charged particles and energetic radiation into space. They are powered by supermassive black holes, weighing in at billions of solar masses. Gas falling into the black hole accumulates in a bright, whirling accretion disc; the jets are probably produced by strong magnetic fields. Quasars are most conspicuous when one of the jets is more or less aimed at the observer. Seen edge-on, their energetic radiation can be obscured by thick clouds of surrounding dust.
Black holes don't emit light. But gas in the neighbourhood of a giant black hole can glow blindingly bright. The result: a quasar — the bright core of a very distant galaxy.