By the end of the 1950s, more important characteristics of Seyfert galaxies were discovered, including the fact that their nuclei are extremely compact (< 100 pc, i.e. "unresolved"), have high mass (≈109±1 solar masses), and the duration of peak nuclear emissions is relatively short (> 108 years).
Ao final da década de 1950, descubríronse as características máis importantes das galaxias Seyfert, incluíndo que os seus núcleos son extremadamente compactos (< 100 pc, é dicir, "non resoltos"), teñen grandes masas (≈109±1 masas solares), e a duración do pico de emisións nucleares é relativamente curto (>108 anos).