@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix dc: <http://purl.org/dc/terms/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<http://astrothesaurus.org/uat/1236>
  skos:editorialNote [ ] ;
  dc:contributor <http://editor.vocabs.ands.org.au/user/AAS_Frey.Katie> ;
  skos:broader <http://astrothesaurus.org/uat/159> ;
  skos:prefLabel "Photon sphere"@en ;
  skos:definition "A surface where if a photon is emitted from one of its points the photon follows a closed orbit and returns periodically to its departure point. Such a surface exists only near sufficiently compact objects where the curvature of space-time is very important. In other words, a body can take a stable orbit around a black hole provided that it moves with the speed of light. However, only photons can have such a velocity; hence the term 'photon sphere.' For a non-rotating Schwarzschild black hole, the photon sphere has a radius of R = 3GM/c2 = 3 RS/2, where G is the gravitational constant, M is the mass, c is the speed of light, and RS is the Schwarzschild radius. For a rotating, Kerr black hole, the situation is much more complex due to the Lense-Thirring effect. In that case circular paths exist for radii whose values depend on the rotation direction. More specifically, in the equatorial plane there are two possible circular light paths: a smaller one in the direction of the rotation, and a larger one in the opposite direction."@en ;
  dc:modified "2020-11-17T19:34:04.939Z"^^xsd:dateTime, "2020-11-17T19:33:55.212Z"^^xsd:dateTime ;
  a skos:Concept .

<http://astrothesaurus.org/uat/159>
  skos:prefLabel "Black hole physics"@en ;
  a skos:Concept ;
  skos:narrower <http://astrothesaurus.org/uat/1236> .