A type of active galaxy characterized by a bright, compact nucleus with strong emission lines in its spectrum. These galaxies have supermassive black holes actively accreting matter, but are less luminous than quasars and show clear spiral structure.
Named after American astronomer Carl Seyfert, who in 1943 first systematically studied these unusual galaxies with bright nuclei and broad emission lines. His work predated the understanding of black holes and active galactic nuclei by decades.
Seyfert galaxies are like quasars' quieter cousins - they have the same supermassive black hole engines, but they're not feeding as voraciously! They're actually quite common, with about 10% of all bright galaxies showing Seyfert characteristics, including some of our nearest galactic neighbors.
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