key term - Active galaxies

Definition

Active galaxies are galaxies that emit an exceptionally high amount of energy from their cores, often due to the presence of a supermassive black hole. They are characterized by their strong and variable emissions across the electromagnetic spectrum.

5 Must Know Facts For Your Next Test

1. Active galaxies include Seyfert galaxies, radio galaxies, and quasars.
2. The central engine of an active galaxy is typically a supermassive black hole with an accretion disk.
3. Active Galactic Nuclei (AGN) can outshine the entire galaxy in which they reside.
4. Jets emitted from active galaxies can travel at relativistic speeds and extend far beyond the host galaxy.
5. Observations in multiple wavelengths (radio, optical, X-ray) are crucial for studying active galaxies.

Review Questions

Related terms

Quasar:

A very luminous and distant type of active galactic nucleus with strong radio emissions.

Seyfert Galaxy:

A type of spiral or irregular galaxy with a bright nucleus showing strong emission lines.

Supermassive Black Hole:

A massive black hole found at the center of many galaxies, including those with active nuclei.