on Physics in 1958 Ambartsumian presented a report arguing that "explosions in galactic nuclei cause large amounts of mass to be expelled. For these explosions to occur, galactic nuclei must contain bodies of huge mass and unknown nature. From this point forward active galactic nuclei (AGN) became a key component in theories of galactic evolution." His idea was initially received skeptically.

A major breakthrough was the measurement of the redshift of the quasar 3C 273 by