disk

The dynamics of a rotating disk (astrophysical disk) consisting of gravitationally-bound gas, dust, and/or objects, is relevant to a number of areas of astrophysics, which can borrow disk-model notions from each other. Such disks include circumstellar disks, ring systems, accretion disks (which might be circumstellar but also might surround black holes), and galactic disks. Thus, for example, physics developed for stellar dynamics within disk galaxies may be found applicable to protoplanetary disks and planet formation. Examples of this are the concepts of Lindblad torque and corotation resonance. More astrophysical terms for various classes of such disks:

• alpha disk
• advection dominated accretion flow
• circumplanetary disk
• debris disk
• decretion disk
• Keplerian disk
• magnetically arrested disk
• transitional disk

Some structural characteristics of disks, such as asymmetry, blobs, rings, and/or spiral arms may indicate bodies (planets, in the case of circumstellar disks, or moons, if surrounding a planet) and/or may indicate gravitational instabilities.