Cosmic Horseshoe

The Cosmic Horseshoe is the nickname given to a gravitationally lensed system of two galaxies in the constellation Leo.

SDSS J114833.14+193003.2
The Cosmic Horseshoe taken using the Wide Field Camera 3 of the Hubble Space Telescope.
Observation data (J2000 epoch)
Constellation	Leo
Right ascension	11h 48m 33.1s[1]
Declination	19° 30′ 03″[1]
Redshift	0.4457 (foreground galaxy) 2.379 (lensed galaxy)[1]
Distance	5.628 Gly (1.726 Gpc) (foreground galaxy) 18.884 Gly (5.790 Gpc) (lensed galaxy)h−1 0.696[1]
Apparent magnitude (B)	20.3[1]
Characteristics
Type	E (Luminous red galaxy) (foreground galaxy)
Mass	5.2 trillion M☉
Notable features	Gravitationally lensed system
Other designations
SDSS J114833.14+193003.2

The Cosmic Horseshoe

The foreground galaxy lies directly in front in the line of sight to a more distant galaxy. 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.

The foreground galaxy, LRG 3-757, is found to be extremely massive, with a mass a hundred times that of the Milky Way 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 by an international team of scientists^[2] using the comprehensive Sloan Digital Sky Survey and is greatly studied by the Hubble Space Telescope.