Canaris Einstein Ring

Q) What theory of Relativity says?

A) Albert Einstein theorized that the fabric of space-time was not rigid, but flexible, like the surface of a trampoline. A massive object, in this case a foreground galaxy, can bend space the way a bowling ball bends the fabric of the trampoline. That bend causes any light from background objects to curve around the foreground object instead of traveling in a straight line — and if the two objects are perfectly lined up, the background galaxy will appear as a circle surrounding the foreground, or lens, galaxy, in what scientists call an "Einstein ring." 

Canaris Einstein Ring:-

The images show that the Einstein Ring, now known as the "Canarias Einstein Ring," is one of the most symmetrical rings yet, meaning that the source galaxy and the lens galaxy are almost perfectly aligned. They're separated by a mere 0.2 arcseconds — a distance 150 times smaller than the apparent size of the full moon. Although their apparent distance in the sky may be small, their physical distance is vast. The two are physically separated by 4 billion light-years. 

"Studying these phenomena gives us especially relevant information about the composition of the source [background] galaxy, and also about the structure of the gravitational field and of the dark matter in the lens [foreground] galaxy,"