Large collections of mass can cause light that passes nearby to bend, called a gravitational lens. By studying the way that the passing light is bent by these large masses, researchers can better understand the properties of these large masses. This article considers the large mass associated with a galaxy and the resulting gravitational lens, helping astronomers to better understand this phenomenon.

http://www.raa-journal.org/raa/index.php/raa/article/view/1275