The Cosmic Horseshoe is the nickname given to a gravitationally lensed system of two very distant galaxies in line in the constellation Leo.
The foreground galaxy at a distance of 5,2 billion light-years lies directly in front in our line of sight to a more distant galaxy at a distance of 10,3 billion light-years.
Due to the passage of the light from the background galaxy through the gravity field of the foreground galaxy, the background galaxy's light is lensed by the warped spacetime environment of the foreground galaxy.
Thus giving the background galaxy a warped appearance.
Unlike most lensed galaxies, the shape of the lensed light of this background galaxy appears shaped like a horseshoe, a 300 degree ring with a diameter of 10 arc-sec.
The total brightness of the ring is mag 20,3 in blue. The foreground red galaxy, LRG 3-757, is found to be extremely massive, with a mass a hundred times that of our galaxy.
It is notable because it belongs to a rare class of galaxies called luminous red galaxies, which has an extremely luminous infrared emission.
The system was discovered in 2007.
Find here the Hubble image.
LRGB (600-140-140-140 min) total 17 h, north is up, seeing 0.8-1.2 arc-sec,
80cm f/7 Astrooptik Keller cassegrain, FLI PL-16803, Astrodon gen2 filters, Prompt 7 CTIO Chile
Processing: Johannes Schedler
Find here the wide image in 25/100% size, a crop on the ring in 140% size below and a animation showing a comparison with Hubble in 320% size.