Approaching the Photon Sphere
As before, from this orientation, the black hole’s enormous gravity bends light to make two discernible images of the constellation Orion. You now descend to the photon sphere. A photon sphere is a location where gravity is so strong that light can travel in circles. Photons orbit the black hole at the distance of the […] The post Approaching the Photon Sphere appeared first on NASA Science .
As the APOD image showcases, the black hole's immense gravity warps light to create two visible images of the constellation Orion. In this particular view, the astronaut descends towards the photon sphere. This region is unique due to its gravitational intensity, allowing light to orbit the black hole in a circular path. At the photon sphere, a photon could travel from the back of the observer's head, circle the black hole once, and return to the eye, enabling the observation of the back of one's head.
The sky once visible to the astronaut now appears behind them, compressed to half its original size. A critical aspect of the photon sphere is that any light emitted from a location outside the sphere cannot reach the observer from beneath, thus giving the impression of looking into the black hole's vast emptiness. For those interested in delving deeper, a virtual trip to black holes and neutron stars is available, as well as accessing the American Journal of Physics article on this subject.
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