seyfert galaxy

noun Astronomy.

1. one of a group of spiral galaxies with compact, bright nuclei having characteristically broad emission lines suggestive of very hot gases in violent motion at the center.

noun

1. any of a class of spiral galaxies having a very bright nucleus, possibly corresponding to an active period in the lives of all spiral galaxies

1. A spiral galaxy with a small, compact, bright nucleus that exhibits variable light intensity and radio-wave emission. Seyfert galaxies are active galaxies and are thought to contain a black hole in their galactic nucleus. The nuclei of Seyfert galaxies generate an emission spectrum characteristic of hot, ionized clouds of gas, shooting out from the accretion disk around the black hole. The observations during the 1940s of American astronomer Carl Seyfert (1911-60), after whom the galaxies are named, demonstrated that these jets of gas are expelled from the nucleus at speeds up to millions of miles per hour. See also blazar quasar.