Active galactic nuclei (AGN)

Definition

Active galactic nuclei (AGN) are extremely energetic regions at the centers of some galaxies, powered by supermassive black holes. They emit vast amounts of radiation across the electromagnetic spectrum, often outshining the rest of the galaxy.

5 Must Know Facts For Your Next Test

1. AGN are thought to be powered by accretion of material onto supermassive black holes located at their centers.
2. They can emit radiation across the entire electromagnetic spectrum including radio, optical, X-ray, and gamma-ray wavelengths.
3. Quasars are a type of AGN known for their exceptional brightness and high redshift values.
4. The immense energy output from AGN is due to gravitational energy being converted into electromagnetic energy as matter spirals into the black hole.
5. AGN can influence galaxy evolution by regulating star formation through feedback mechanisms like jets and winds.

Review Questions

• What powers an active galactic nucleus?
• How do AGN affect their host galaxies?
• What distinguishes quasars from other types of AGN?

Related terms

Quasar:

A highly luminous type of AGN with significant redshift, indicating they are very distant and thus seen as they were in the early universe.

Supermassive Black Hole:

A black hole with a mass ranging from millions to billions of times that of our Sun, typically found at the centers of galaxies.

Accretion Disk:

The disk-shaped flow of gas, dust, and other material that orbits and gradually falls into a central body like a black hole in an AGN.