Quasar
An extremely luminous Active Galactic Nucleus (AGN) powered by gas accreting onto a supermassive black hole at the center of a distant galaxy.
Governing formula
L_quasar ~ 10⁴⁰ W (100–1000 times Milky Way Luminosity)
SI unit
Luminosity / Redshift z
In depth
Short for 'Quasi-Stellar Radio Source'. Infalling matter in the accretion disk converts gravitational energy into intense radiation across the spectrum, outshining its host galaxy and visible across cosmological distances.
Examples in the real world
3C 273, the brightest optical quasar located at a cosmological distance of ~2.4 billion light-years.