Concept
Event Horizon
The point of no return around a black hole.
The boundary of a black hole within which nothing — not even light — can escape to the outside universe.
Overview
The boundary of a black hole within which nothing — not even light — can escape to the outside universe.
See also
Singularity
A point of infinite density inside a black hole.
Photon Sphere
Where light itself can orbit a black hole.
Strömgren Sphere
The ionised bubble around a hot star.
Perihelion
The closest point in an orbit to the Sun.
Aphelion
The farthest point in an orbit from the Sun.
Perigee
The closest point in an Earth-centred orbit.