Galactic gravitational lensing, Hubble Space Telescope image. The blue ring surrounding the galaxy (yellow) is light from another galaxy behind this one. The light from the background galaxy has been lensed by the gravitational field of the foreground galaxy, forming what is known as an Einstein Ring. This galaxy's catalogue name is SDSS J073728.45+321618.5, indicating that it was discovered by the Sloan Digital Sky Survey (SDSS). It is one of eight giant elliptical galaxies with Einstein Rings, all around 2 to 4 billion light years away, that were discovered by the Sloan Lens ACS Survey (SLACS), and announced in November 2005.