Cosmology, Page 95: [Previous Page] [Next Page] [Class Home Page] Textbook pages 450 - 458

Active Galaxies: The Seyfert Galaxies

Active galaxies are characterized by one or more of the following features: a bright compact nucleus, strong and very broad emission lines, intense raio emission, and a peculiar morphology.

Seyfert Galaxies
All these galaxies show the characteristic intense, point-like nucleus originally remarked for this class by Carl Seyfert. The galaxies' Hubble types are also representative for Seyfert galaxies as a group, dominated by early-type spirals (Sa and Sb, with both barred and non-barred representatives) and S0 systems.

Spectra of Seyferts DID show normal lines from typical stars. However, something in the spectrum made these galaxies really stand out: Emission lines of Hydrogen and Helium seen in the nucleus. Moreover, these emission lines are incredibly broad, indicating velocities of thousands of km/s. Something quite unusual is occuring in these galaxies! Click here for a Seyfert 1 spectrum, and here for a Seyfert 2 spectrum.