Fanaroff-Riley 1 and 2 (FR-1 and FR-2) labels come from a classification system developed by B.L. Fanaroff and J.M. Riley that is used to identify radio galaxies with active galactic nuclei based on the brightness of their radio emissions. FR-1’s are radio sources whose luminosity decreases as the distance from the central galaxy host increases and can be signposts for galaxy clusters. FR-II's are sources that exhibit increasing brightness in the outer lobes.

Credit: VLASS (NRAO/AUI/NSF)