photon sphere (English, noun)
expansion: photon sphere (plural photon spheres)
Senses:
topics: astronomy
cosmology
natural-sciences
glosses: Of a black hole, a spherical limit around a black hole at such distance that any photon meeting it tangentially is constrained to travel in a circular orbit; (more loosely) the region between this limit and the event horizon.
Forms:
form: photon spheres
tags: plural