Accretion disk

Definition

An accretion disk is a rotating disk of gas and dust surrounding a massive central object, such as a black hole. It forms as material spirals inward due to gravitational forces and frictional heating causes it to emit electromagnetic radiation.

5 Must Know Facts For Your Next Test

1. Accretion disks are often found around black holes, neutron stars, and supermassive black holes in the centers of galaxies.
2. The intense heat generated by friction within the accretion disk can cause it to shine brightly in X-rays and other wavelengths.
3. Accretion disks play a key role in the growth of black holes by funneling material into them.
4. The presence of an accretion disk is one piece of evidence for the existence of black holes.
5. In active galactic nuclei (AGN) and quasars, the energy emitted from accretion disks can outshine the entire host galaxy.

Review Questions

• What is an accretion disk and what causes it to form?
• How does friction within an accretion disk affect its properties?
• Why are accretion disks important for understanding black holes and quasars?

Related terms

Event Horizon: The boundary surrounding a black hole beyond which nothing can escape its gravitational pull.

Quasar: An extremely luminous active galactic nucleus powered by a supermassive black hole with an accretion disk.

Active Galactic Nucleus (AGN): A region at the center of a galaxy that emits tremendous amounts of energy due to matter accreting onto a supermassive black hole.