Illustration of a black hole in a globular cluster. The presence of the black hole in the foreground can bend the fabric of spacetime, altering the path of light from background stars. The bent light is represented as a diffuse glow around the black hole. Black holes can also appear to glow due to Hawking radiation which occurs at the edge of the black hole, known as the event horizon. Hawking radiation is due to quantum effects involving pairs of photons where one is trapped by the black hole's gravity and the other escapes into the Universe. Globular clusters are collections of stars that are bound together by gravity.