A circumstellar disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form. Around mature stars, they indicate that planetesimal formation has taken place and around white dwarfs, they indicate that planetary material survived the whole of stellar evolution. Such a disk can manifest itself as:
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Young star
- Nebular hypothesis
- Accretion disk is a circumstellar disk feeding material onto the central star. This is how young stars accumulate their mass. The accretion disk phase lasts a few to 10 million years. Accretion rates are typcially 10-7 to 10-9 solar masses per year but can vary.
- Protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a newly formed star. It may contain a few percent of the mass of the central star mainly in the form of gas which is itself mainly hydrogen.
Belt or cloud
- Asteroid belt is a reservoir of small bodies in our Solar System located between the orbit of Mars and Jupiter. It is a source of interplanetary dust.
- Edgeworth-Kuiper belt
- Öpik- Oort cloud / Hills Cloud, only the inner Oort cloud is toroid-like shape. The outer Oort cloud is more spherical in shape.
Binary system
- Circumprimary disk, is where a disk orbits the primary (ie. more massive) star of the binary star system.[1]
- Circumsecondary disk is one around the secondary (i.e. less massive) star of the binary star system.
- Circumbinary disk, is where a disk orbits both the primary and the secondary of the binary system.
Dust
- Debris disk consists of planetesimals along with fine dust and small amounts of gas generated through their collisions and evaporation. The original gas and small dust particles have been dispersed or accumulated into planets.[2]
- Zodiacal Light or interplanetary dust is the material in the Solar System created by collisions of asteroids and evaporation of comet seen to observers on Earth as a band of scattered light along the ecliptic before sunrise or after sunset.
- Exozodiacal dust is dust around another star than the Sun in a location analogous to that of the Zodiacal Light in our own Solar System.
See also
References
- ^ Discovery of a New Companion and Evidence of a Circumprimary Disk: Adaptive Optics Imaging of the Young Multiple System VW Chamaeleon, Brandeker, Alexis et al. 2001
- ^ Klahr, Hubert; Brandner, Wolfgang (2006). Planet Formation. Cambridge University Press. pp. 25. ISBN 0521860156.
External links
- McCabe, Caer (May 30 2007). "Catalog of Resolved Circumstellar Disks". NASA JPL. http://www.circumstellardisks.org/. Retrieved 2007-07-17.en:Circumstellar disk
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