What is Accretion disk?
[[Image:Accretion disk.jpg|thumb|right|200px|Artist's conception of a [[binary star]] system with one [[black hole]] and one main sequence [[star]].]] An '''accretion disk''' (or '''disc''') is an [[Astronomy|astronomical]] term. It describes a disc of material being drawn in by [[gravity]] to a [[centre of mass]], such as a [[star]] or [[black hole]]. As the material comes in, it spins round the central body and [[Electromagnetic radiation|radiates]] [[energy]]. The central body is typically either a young star, a [[protostar]], a [[white dwarf]], a [[neutron star]], or a [[black hole]]. As the material moves in, gravitational energy released in that process is transformed into heat and [[rotation]]al movement. The energy emitted at the disk surface is in form of electromagnetic radiation. The frequency range of that radiation depends on the central object. Accretion discs of young stars and protostars radiate in the [[infrared]], those around neutron stars and black holes in the [[X-ray]] part of the [[spectrum]]. ==Other websites== * [http://astsun.astro.virginia.edu/~jh8h/ Professor John F. Hawley homepage] {{Webarchive|url=https://web.archive.org/web/20070919040509/http://astsun.astro.virginia.edu/~jh8h/ |date=2007-09-19 }} * [http://www.astro.virginia.edu/VITA/papers/nraf2/section1.html Nonradiative Black Hole Accretion] {{Webarchive|url=https://web.archive.org/web/20100723182955/http://www.astro.virginia.edu/VITA/papers/nraf2/section1.html |date=2010-07-23 }} * [http://www.scholarpedia.org/article/Accretion_Discs Accretion Discs on Scholarpedia] * [http://www.newscientistspace.com/article.ns?id=mg19025574.600&feedId=online-news_rss20 Magnetic fields snare black holes' food] - New Scientist {{physics-stub}} {{DEFAULTSORT:Accretion Disk}} [[Category:Astrophysics]] [[Category:Binary stars|-]] [[Category:Black holes]]