Intrinsic redshift is the hypothesis from various non-standard cosmologies that a significant portion of the observed redshift of extragalactic objects (e.g. quasars and galaxies) may be caused by a phenomenon other than the traditionally accepted redshift mechanisms – (1) cosmological redshift; (2) Doppler redshift; and (3) gravitational redshift.
The main proponent of the intrinsic redshift hypothesis is astronomer Halton Arp, who noted that many of the astronomical radio sources close to radio galaxies were quasars — high redshift objects a minority of which are radio-loud. In some instances these quasars seemed aligned in pairs across the radio galaxies. Arp proposed the hypothesis that the quasars might be associated with the radio galaxies which themselves somehow ejected the quasars from the galactic nucleus. Quasars which followed this model are described as "local" and by extension their redshifts would not follow Hubble's law.
Since radio galaxies have much lower observed redshifts than the quasars, the excess quasar redshift could not have a Doppler origin from high ejection velocities because there are no blueshifted quasars with respect to the objects from which they are proposed to have originated. Since the traditionally accepted redshift mechanisms are not capable of explaining the large observed redshifts of quasars if they are associated with relatively nearby radio galaxies, Arp concluded that most of the observed redshift of the quasars must be caused by an unknown non-cosmological or "intrinsic" mechanism.
Other astronomers that have also published research supporting the hypothesis that at least some quasars are local rather than at cosmological distances include:
