Astrophysics (Index)About

circumstellar disk

(disk or ring shaped accumulation of matter around a star)

A circumstellar disk (in context, just disk) is matter, typically in a ring, collected around a star. It can be composed of gas, dust, planetesimals, or a combination, in orbit around the star. For young stars, for which the term protoplanetary disk is used, it may be the raw material of later planets. The asteroids around the Sun represent a thin circumstellar disk.

Excess infrared from a star is evidence of a disk, indicating black-body radiation for something large and cooler than the star. When the disk can be resolved, the material making up the disk and how it varies by radius can be determined from this electromagnetic radiation, which is affected by the dust grain size: the emission of grains is inefficient for wavelengths long in comparison to the grain's diameter.

Older stars can also have such disks, such as debris disks.

(disk type,object type,stars)
Further reading:

Referenced by pages:
amateur astronomy
Be star
circumplanetary disk
Coriolis force
corotation torque
dead zone
debris disk
extra-solar planet
GG Tau
gravitational instability (GI)
Hall effect
infrared excess (IRX)
Keplerian disk
Kepler radius
Lindblad torque
Lyot coronagraph (CLC)
mass transport
Maxwell-Boltzmann distribution
nebular hypothesis
planetary system
planet formation
Poynting-Robertson effect
protoplanetary disk (PPD)
radiation pressure
Roche limit
shell star (sh)
spiral arm
spiral density wave
surface density (Σ)
transitional disk
young stellar object (YSO)