The James Webb Space Telescope (JWST) has captured an image of an Einstein ring, a rare optical illusion caused by gravitational lensing. The image was released by the European Space Agency (ESA) and the Canadian Space Agency as their March picture of the month.
The ring-like structure is a result of light from a distant galaxy being bent around a massive elliptical galaxy in the foreground. The central bright region represents the nearer galaxy, while the stretched orange and blue arcs surrounding it are the distorted light from a more distant spiral galaxy.
Gravitational lensing occurs when a massive object, such as a galaxy or black hole, bends the light of a more distant source. This effect is a consequence of Einstein’s theory of relativity, which explains how mass warps space-time and alters the path of light.
For an Einstein ring to form, the observer, the lensing galaxy, and the background light source must be precisely aligned. Such perfect alignment is rare, making these phenomena valuable for astronomical research.
In this instance, the elliptical galaxy—part of the galaxy cluster SMACSJ0028.2-7537—is so massive that it bends and magnifies the light from the more distant spiral galaxy behind it. Despite the warping, individual star clusters and gas structures remain visible.
Gravitational lensing helps astronomers study distant and faint galaxies that would otherwise be undetectable. Light from these galaxies, emitted billions of years ago, provides insights into the early universe and the formation of some of the first galaxies after the Big Bang.
Since black holes and dark matter do not emit light, scientists use gravitational lensing to detect and study these invisible phenomena. By analysing how background light is bent, researchers can infer the presence and distribution of unseen cosmic structures.