This fascinating galaxy was originally discovered by William Herschel on March 20, 1787. Herschel recorded his discovery as two separate objects, H176 and H177 in his so-called Class I catalog of bright nebulae, but noted that these two objects joined to form the “letter S.” These two Herschel entries were later recorded in the New General Catalog as NGC4656 and NGC4657, with the main elongated body of the galaxy being NGC4656 (with an evident bright core roughly centered) and the hooked “blade of the hockey stick” on the NE end being NGC4657. This has evidently led to some confusion regarding the nature of this galaxy, as some sources (e.g., the New General Catalog) continue to list NGC4657 as a separate irregular galaxy, when it is most likely a highly active star forming region within NGC4656. This star forming activity and peculiar hook shape are thought to be the result of tidal interaction between NGC4656 and NGC4631, the so-called Whale Galaxy located approximately half a degree to the NW (not seen in the image). NGC4656 and NGC4631 are currently separated by about 145,000 light years, and these galaxies are members of the NGC4631 group of galaxies located approximately 29 million light years from Earth. NGC4656 is a fairly large galaxy, with estimates ranging from 75,000 to 91,000 light years in diameter.

There is a dwarf galaxy located further the NE from the hook, which can be seen in this image as a faint, diffuse blue cloud. Astronomers believe this is a separate dwarf galaxy, and it has been labelled NGC4656UV because it emits strong ultraviolet radiation. There have been studies to understand this dwarf galaxy. In a 2012 paper, Schechtman-Rook and Hess presented an argument that NGC4656UV may be a Tidal Dwarf Galaxy (TDG) formed as a result of tidal interaction between NGC4656 and NGC4631. However, in 2017 Zasov, Saburova, Egorov, and Uklein presented data in support of NGC4656UV being a separate member of the NGC4631 galaxy cluster, currently in tidal interaction with NGC4656 but not resulting from this interaction. (Here are links to the articles mentioned: iopscience.iop.org/article/10.1088/0004-637X/750/2/171/pdf and export.arxiv.org/pdf/1705.03523)