photon sphere

English

Etymology

photon +‎ sphere. From being a spherical region around a black hole, where photons travel in circular orbits, instead of hyperbolic ones.

Noun

photon sphere (plural photon spheres)

1. (of a black hole) A region of around a black hole where photons travel in orbits around the singularity, just beyond the event horizon.

Synonyms

• photon circle
• last photon orbit

Coordinate terms

• accretion disc
• black hole
• black hole jet
• ergosphere
• event horizon
• Roche limit
• singularity

See also

• photosphere (a part of a star, that forms the visible disc/surface of the star)

Further reading

• photon sphere on Wikipedia.Wikipedia