Abell 370 is a galaxy cluster located nearly 5 billion light-years away from the Earth (at redshift z = 0.375), in the constellation Cetus. Its core is made up of several hundred galaxies. It was catalogued by George Abell, and is the most distant of the clusters he catalogued.
In the 1980s astronomers of Toulouse Observatory discovered a gravitational lens in space between Earth and Abell 370 using the Canada-France-Hawaii Telescope. A curious arc had been observed earlier near the cluster, but the astronomers were able to recognize it as this phenomenon.
Gravitational lensing Abell 370 appears to include several arcs of light, including the largest ever discovered at 30" long. It was originally referred to as the Giant Arc, but later renamed to the Dragon Arc. These arcs or deformations are mirages caused by gravitational lensing of distant galaxies by the massive galaxy cluster located between the observer and the magnified galaxies.New York Times, "SCIENCE WATCH; Mirages in the Sky May Not Be So Rare" Tuesday, October 18, 1988 This cluster shows an apparent magnitude of +22.
In 2002, astronomers used this lensing effect to discover a galaxy, HCM-6A, 12.8 billion light years away from Earth. At the time it was the furthest known galaxy.BBC News, "Far away stars light early cosmos" Thursday, 14 March 2002, 11:38 UTC
In 2009, an HST study in the field of Abell 370 revealed in greater detail the 30" long arc with the appearance of a dragon, and hence rebranded as The DragonAstronomy Now, "Refurbished Hubble gets off to a flying start" 09-09-09 (accessed 2009-11-07) by NASA scientists.New York Times, "The Universe, in High Definition" 09/09/09 (accessed 2009-11-07) Its head is composed of a spiral galaxy,New Scientist, "Upgraded Hubble telescope spies cosmic 'dragon' " 09.09.09 (accessed 2009-11-07) with another image of the spiral composing the tail. Several other images form the body of the dragon, all overlapping.National Geographic, "NEW HUBBLE PICTURES: First Shots From Upgraded Orbiter" Saturday, November 7, 2009 (accessed 2009-11-07) These galaxies all lie approximately 5 billion light years away.
See also Abell 2218 Abell catalogue List of Abell clusters
References
Gravitationally lensed images in Abell 370 Authors: Grossman, S. A. & Narayan, R. Image of Abell 370 released bu STScI HST in May 2017 : A Lot of Galaxies Need Guarding in This NASA Hubble View
External links
A lot of galaxies need guarding in this NASA Hubble view