NGC 772
NGC 772 is a large unbarred spiral galaxy approximately 106 million light-years away in the constellation Aries. It was discovered by German-British astronomer William Herschel on 29 November 1785.
Characteristics
At around 200,000 light years in diameter, NGC 772 is somewhat larger than the Milky Way Galaxy, and is surrounded by several satellite galaxies – including the dwarf elliptical, NGC 770 – whose tidal forces on the larger galaxy have likely caused the emergence of a single elongated outer spiral arm that is much more developed and stronger than the other arms. Halton Arp includes NGC 772 in his Atlas of Peculiar Galaxies as Arp 78, where it is described as a "Spiral galaxy with a small high-surface brightness companion".NGC 772 probably has a H II nucleus, but it may be a transitional object.