Changes

==Etymology==

==Etymology==

[[Latin]] accretion-, accretio, from accrescere  

[[Latin]] accretion-, accretio, from accrescere  

*Date: [http://www.wikipedia/org/wiki/17th_Century 1615]

*Date: [https://www.wikipedia/org/wiki/17th_Century 1615]

==Definitions==

==Definitions==

*1 : the process of growth or enlargement by a gradual buildup: as a : increase by external addition or accumulation (as by adhesion of external parts or particles) b : the increase of land by the action of natural forces

*1 : the process of growth or enlargement by a gradual buildup: as a : increase by external addition or accumulation (as by adhesion of external parts or particles) b : the increase of land by the action of natural forces

*2 : a product of accretion; especially : an extraneous addition <accretions of grime>

*2 : a product of accretion; especially : an extraneous addition <accretions of grime>

==Description (Physics)==

==Description (Physics)==

An '''accretion disc''' is a [[structure]] (often a circumstellar disk) formed by [[diffuse]] [[material]] in orbital [[motion]] around a central [[body]]. The central body is typically a young [[star]], a [http://en.wikipedia.org/wiki/Protostar protostar], a [http://en.wikipedia.org/wiki/White_dwarf white dwarf], a [http://en.wikipedia.org/wiki/Neutron_star neutron star], or a [http://en.wikipedia.org/wiki/Black_hole black hole]. [[Gravity]] causes material in the disc to spiral inward towards the central body. Gravitational [[forces]] compress the material causing the emission of [http://www.wikipedia.org/wiki/Electromagnetic_Radiation 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]].[http://en.wikipedia.org/wiki/Accretion_disk]

An '''accretion disc''' is a [[structure]] (often a circumstellar disk) formed by [[diffuse]] [[material]] in orbital [[motion]] around a central [[body]]. The central body is typically a young [[star]], a [https://en.wikipedia.org/wiki/Protostar protostar], a [https://en.wikipedia.org/wiki/White_dwarf white dwarf], a [https://en.wikipedia.org/wiki/Neutron_star neutron star], or a [https://en.wikipedia.org/wiki/Black_hole black hole]. [[Gravity]] causes material in the disc to spiral inward towards the central body. Gravitational [[forces]] compress the material causing the emission of [https://www.wikipedia.org/wiki/Electromagnetic_Radiation 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]].[https://en.wikipedia.org/wiki/Accretion_disk]

[[Category: Physics]]

[[Category: Physics]]

[[Category: General Reference]]

[[Category: General Reference]]