What are Quasars? – Science ABC, Quasars inhabit the centers of active galaxies and are among the most luminous, powerful, and energetic objects known in the universe, emitting up to a thousand times the energy output of the Milky Way, which contains 200–400 billion stars.
They were called quasi-stellar radio sources (shortened to quasars) when they were detected with radio telescopes. They emit tremendous amounts of energy from very small volumes. The most distant quasars seen are so distant that they are receding at more than 90 percent of the speed of light.
Quasars emit large amounts of radio energy.
The quasar $3 mathrm{C} 273$ has a luminosity of $10^{12} L_{text {sun }}$. Assuming that the total luminosity of a large galaxy, such as the Andromeda Galaxy, is 10 billion times that of the Sun, compare the luminosity of $3 mathrm{C} 273$ with that of the entire Andromeda Galaxy.
