A stunning new image from the James Webb Space Telescope reveals a cosmic illusion called an Einstein ring, where the light from a distant galaxy is distorted into a perfect circle by the gravity of a closer galaxy.
Cosmic optical illusion: Einstein ring
This month's new image from the James Webb Space Telescope shows a rare and striking cosmic phenomenon called an Einstein Ring. At first glance, it might look like a single, oddly shaped galaxy—but it's actually two galaxies separated by a great distance. The closer galaxy is in the center of the image, and light from a more distant galaxy is bent around it, creating a glowing ring.
Einstein rings appear because of a process called gravitational lensing, in which light from a distant object is bent by the gravity of a massive object between it and the observer. This happens because spacetime, the very fabric of the universe, is curved by mass, and light travels along these curves. This curvature is too weak to be noticeable on an everyday scale, but on an astronomical scale it becomes dramatic, for example when light from one galaxy passes by another galaxy or cluster of galaxies.
Perfect alignment creates the rings
When the background galaxy, the lensing galaxy, and the observer are nearly perfectly aligned, the lensing effect creates a nearly perfect circle of light: an Einstein ring. Depending on how precise the alignment is, the ring can appear complete, as here, or only partially. These rare alignments act as natural magnifying glasses, allowing astronomers to study very distant and faint galaxies that would otherwise be invisible.
The lensing galaxy at the center of this Einstein ring is an elliptical galaxy, as can be seen from its bright core and smooth, featureless body. This galaxy belongs to a galaxy cluster called SMACSJ0028.2-7537. The reshaped galaxy that surrounds the elliptical galaxy is a spiral galaxy. Although its image has been distorted as its light travels around the elliptical galaxy, individual star clusters and gas structures can be clearly seen.
Mapping the Universe with Webb and Hubble
The data for this image were collected as part of the Strong Lensing and Cluster Evolution Survey (Program 5594), led by Guillaume Mahler of the University of Liège in Belgium. The project involves astronomers from various countries using Webb's Near-Earth Camera to study how galaxy clusters have evolved over the past eight billion years. The study observes 182 galaxy clusters. This image also includes data from two instruments on the Hubble Space Telescope: the Wide Field Camera 3 and the Advanced Camera for Surveys.
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