Such "Einstein rings" are very rare, though, and have only been observed in a very few cases.

When both galaxies are exactly lined up, the light forms a circle, called an "Einstein ring," around the foreground galaxy.

The light bent by a dark-matter-dominated galaxy can form what is known as an "Einstein ring"

Note that in order for a distributed mass to result in an Einstein ring, it must be axially symmetric.

This geometry is so rare that until last week only three complete Einstein rings were known.

The size of an Einstein ring is given by the Einstein radius.

The first Einstein ring corresponds to the most distorted region of the picture and is clearly depicted by the galactic disc.

The Einstein ring is an example of the deflection of light from distant galaxies by more nearby objects.

An extremely unusual cosmic phenomenon predicted by Einstein, an Einstein ring, has apparently been observed by radio astronomers.

Obviously, relativistic Einstein rings are relativistic images for the case when the source, lens, and observer are aligned.