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.

In the 1980s astronomers of Toulouse Observatory discovered a gravitational lens in space between Earth and Abell 370 using the Canada-France-Hawaii Telescope.

[4][5] A curious arc had been observed earlier near the cluster, but the astronomers were able to recognize it as this phenomenon.

In 2002, astronomers used this lensing effect to discover a galaxy, HCM-6A, 12.8 billion light years away from Earth.

[9] In 2009, and 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 Dragon[10] by NASA scientists.