Active Galactic Nucleus

Definition

An active galactic nucleus (AGN) is the bright, central region of a galaxy that is powered by a supermassive black hole actively accreting matter. AGNs are some of the most luminous and energetic objects in the universe, emitting intense radiation across the electromagnetic spectrum.

5 Must Know Facts For Your Next Test

1. Active galactic nuclei are thought to be powered by the accretion of matter onto supermassive black holes at the centers of galaxies.
2. The intense radiation emitted by AGNs can outshine the entire host galaxy, making them some of the most luminous objects in the universe.
3. AGNs can be classified into different types based on their observational properties, such as Seyfert galaxies, quasars, and blazars.
4. Galaxy mergers and interactions can trigger the formation of an active galactic nucleus by funneling gas and dust towards the supermassive black hole at the center.
5. The study of active galactic nuclei provides insights into the growth and evolution of supermassive black holes and their host galaxies.

Review Questions

• Explain how the presence of a supermassive black hole at the center of a galaxy is related to the formation of an active galactic nucleus.
  • The supermassive black hole at the center of a galaxy is the driving force behind the formation of an active galactic nucleus. As matter, such as gas and dust, is accreted onto the black hole, it heats up and emits intense radiation across the electromagnetic spectrum. This accretion process powers the active galactic nucleus, making it one of the most luminous and energetic objects in the universe. The supermassive black hole is the engine that fuels the active galactic nucleus, and the study of AGNs provides valuable insights into the growth and evolution of these massive black holes and their host galaxies.
• Describe the role of galaxy mergers and interactions in the formation and evolution of active galactic nuclei.
  • Galaxy mergers and interactions can play a crucial role in the formation and evolution of active galactic nuclei. When two or more galaxies collide, the gravitational interactions can funnel large amounts of gas and dust towards the center of the merged galaxy, where the supermassive black hole is located. This increased supply of matter can then be accreted by the black hole, triggering the formation of an active galactic nucleus. The intense radiation and outflows from the AGN can also influence the surrounding galaxy, affecting its star formation and evolution. Therefore, the study of active galactic nuclei in the context of galaxy mergers and interactions provides important insights into the coevolution of supermassive black holes and their host galaxies.
• Analyze how the study of active galactic nuclei contributes to our understanding of the structure and evolution of the Milky Way galaxy, particularly the region at its center.
  • The study of active galactic nuclei, such as those found at the centers of other galaxies, can provide valuable insights into the structure and evolution of the Milky Way galaxy, particularly the region at its center. The Milky Way is known to host a supermassive black hole at its core, called Sagittarius A*. While the Milky Way's central black hole is not currently in an active state, the study of active galactic nuclei in other galaxies can help us understand the potential for our own galaxy's central black hole to become active in the past or future. Additionally, the radiation and outflows from active galactic nuclei can influence the structure and dynamics of the surrounding galaxy, including the central region. By understanding the processes that govern active galactic nuclei, we can better comprehend the role of supermassive black holes in shaping the evolution of galaxies like our own Milky Way.

Related terms

Supermassive Black Hole: An extremely dense and massive black hole, millions to billions of times the mass of the Sun, typically found at the center of galaxies.

Quasar: A highly luminous active galactic nucleus, powered by the accretion of matter onto a supermassive black hole, that can outshine the entire host galaxy.

Galaxy Merger: The collision and combination of two or more galaxies, which can trigger the formation of an active galactic nucleus.