Photon Sphere

      Super-massive objects in space have a photon sphere. This imaginary sphere’s center is rooted at the center of gravity of the object; its radius represents the distance from which the object may, with its impressive gravitational attraction, capture photons—the elementary particles of light—into an orbit.

      Super-massive objects that rotate have two photon spheres when approached, following a line perpendicular to their axis of rotation and incident with their center of gravity. First of all, it must be understood that when super-massive objects rotate, they drag space in the ergosphere around with them (frame-dragging), as a whirlpool twirls the surrounding water. Due to this principle, photons travelling in the same direction as the frame-dragging are moving at the speed of light relative to the ergosphere; while their speed relative to unaffected space, exceeds this value by the speed of the dragged ergosphere (think of running in the same direction as a train and your speed relative to the static platform). As orbits closer to an object must have increasingly greater speeds in order to overcome heightened gravitational influence, the closer photon sphere can exist so near the mass because of the photon’s added alacrity. The other photon sphere is further and its luminous residents behave as if the mass were not rotating.

      It would be spellbinding to see rings of pure light, resembling Saturn’s rocky ones, around a black hole, or a heavy neutron star, captured in an infinite and redundant race around and around, at the speed of light... Unfortunately, we could never witness such a wonder because, in fact, the light goes around forever: it rarely leaves the orbit. For light to be seen, it must reach someone’s eyes, but if it is bound by the dark mysteries of gravity it could never reveal its elegantly strange condemnation.