Einstein ring

plural Einstein rings

1. astronomyA ring-shaped gravitational mirage; an image of a distant light source, such as a galaxy, which has been distorted into a ring by a gravitational lens.

   This is quite a bit larger than the cores in most clusters, so clusters are unlikely to produce dramatic signatures such as Einstein rings.

   2017, Scott Dodelson, Gravitational Lensing, Cambridge University Press, page 48

   2 more examples

   Thus, clusters of galaxies with masses M ∼ 10¹⁵M_⊙ at cosmological distances can result in Einstein rings with angular radii tens of arcseconds.

   2008, Malcolm Longair, Galaxy Formation, 2nd edition, Springer, page 130

   The many constraints that the images of Einstein rings provide, allow us to determine the slope of the mass distribution in the lensing galaxy. In 1988, the first example of an "Einstein ring" was discovered by Jackie Hewitt [Hew].

   2012, Arlie O. Petters, Harold Levine, Joachim Wambsganss, Singularity Theory and Gravitational Lensing, Springer, page 155