Carl Seyfert was an American astronomer known for his significant contributions to the study of galaxies. He is best recognized for identifying a specific type of galaxy, now called Seyfert galaxies, which are characterized by their bright centers and active nuclei. His work in the 1940s helped lay the groundwork for understanding the nature of these galaxies and their role in the universe. Seyfert's research focused on the emission lines in the spectra of these galaxies, which indicated the presence of supermassive black holes at their centers. His findings have had a lasting impact on the field of astrophysics and have influenced subsequent studies of active galactic nuclei and the evolution of galaxies.