Seyfert

Definition

Seyfert galaxies are a class of active galaxies with extremely bright nuclei, believed to be powered by supermassive black holes. They exhibit strong emission lines in their spectra, indicating high-energy processes at their cores.

5 Must Know Facts For Your Next Test

1. Seyfert galaxies are one of the two largest groups of active galactic nuclei (AGN), the other being quasars.
2. They were first identified by Carl Seyfert in 1943 based on their unique spectral characteristics.
3. Seyfert galaxies are divided into two types: Type I Seyferts have broad and narrow emission lines, while Type II Seyferts only show narrow lines.
4. The brightness of Seyfert nuclei can vary significantly over short timescales, suggesting the energy source is compact.
5. They are typically found in spiral galaxies and make up about 10% of all known galaxies.

Review Questions

• What distinguishes Type I Seyfert galaxies from Type II?
• Who first identified Seyfert galaxies and in what year?
• How do the emission lines in Seyfert galaxy spectra indicate active galactic nuclei (AGN)?

Related terms

Quasar:

A highly luminous AGN with powerful radiation output across the electromagnetic spectrum.

Active Galactic Nucleus (AGN): A region at the center of some galaxies that emits an extraordinary amount of energy due to a supermassive black hole.

Supermassive Black Hole:

An enormous black hole, often millions to billions of times the mass of our Sun, located at the centers of most large galaxies.