Blindingly luminous galactic nuclei powered by supermassive black holes devouring infalling matter.
Core Principles & Analysis
Maarten Schmidt cracked the mystery in 1963 by recognizing 3C 273's strange spectrum as hydrogen lines redshifted 16%, placing it billions of light-years away.
3C 273 shines with about 4 trillion Suns' luminosity; at 33 light-years it would rival the Sun in our sky.
The most distant known quasars shine from under 700 million years after the Big Bang, already hosting billion-solar-mass black holes.