NGC 646 is a large barred spiral galaxy located in the constellation Hydrus.[2] Its speed relative to the cosmic microwave background is 8,145 ± 19 km/s, which corresponds to a Hubble distance of 120.1 ± 8.4 Mpc (~392 million ly). NGC 646 was discovered by British astronomer John Herschel in 1834.[3] It forms an interacting galaxy pair.[4]
The Hubble distance of PGC 6014, the galaxy to the east of NGC 646, is 106.4 ± 7.5 Mpc (~347 million ly).[5] A distance of approximately 45 million light years therefore separates these two galaxies which appear to be neighbors in the image. Their gravitational interaction, if there is any interaction, should therefore be of short duration.[6]
