Photos snapped by the James Webb Space Telescope have revealed the farthest ever example of an Einstein ring. The recordbreaking halo of warped light, which is a whopping 21 billion light years away, is unusually perfect and surrounds a mysteriously dense galaxy. An Einstein ring is an extremely rare type of gravitationally lensed object that was first predicted by Albert Einstein’s theory of relativity.
Gravitational lensing occurs when the immense gravity of a massive foreground object, such as a galaxy cluster or black hole, warps space-time around itself; light emitted by more distant objects, such as galaxies or supernovae, that passes through this warped space-time also appears curved and warped from our perspective on Earth. This effect also magnifies the light of the object being lensed, similar to how a magnifying glass works, allowing astronomers to study distant objects in greater detail than is normally possible. Most gravitationally lensed objects form arcs or partial rings that surround the foreground object. But a true Einstein ring forms a complete circle around the closer entity, possible only when the distant object, foreground object and observer are perfectly aligned.