Tidal Streams in NGC 770, NGC 772 (Arp 78) - Interacting galaxies in Aries

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NGC 770 is a low-luminosity elliptical companion to the large spiral galaxy NGC 772 and is the brightest satellite galaxy identified in this system by Zaritsky et al. (1997). The parent spiral galaxy, NGC 772, has an absolute magnitude MB=-21.6 and is listed in the Atlas of Peculiar Galaxies (Arp 78; Arp 1966). This system has been included in many studies of interacting systems (e.g., Pignatelli et al. 2001; Tutui & Sofue 1997; Elmegreen et al. 1991; Laurikainen & Moles 1989) because of a prominent asymmetric spiral arm and faint trails of surrounding material. (NGC 770: A counterrotating core in a low-luminosity elliptical galaxy - M. Geha et al.)

NGC 772 (also known as a peculiar spiral galaxy Arp 78) is an unbarred giant spiral galaxy approximately 106 million light-years away in the constellation Aries. It is notable for possessing a single elongated outer spiral arm. The asymmetric spiral arms are distorted by interaction with the dwarf elliptical galaxy NGC 770 (Cappellari et. al "The Atlas3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria"). NGC 770 appears to be at about the same distance as NGC 772, so it is most likely a true companion to the larger spiral system. It has a separation of only 160 000 light-years from its larger companion with an actual diameter of only about 40 000 light-years. NGC 772 is huge, having a diameter of 208 000 lightyears, making it twice the diameter of our Milky Way Galaxy. Stars oust outward from NGC 770 appear as a fine haze extending away from the pair. NGC772 is surrounded by several satellite galaxies and additionally, this field has many smaller galaxies.

At least two supernovae have appeared in this galaxy: sn2003hl and sn2003iq. Each of these supernovae was a type II supernova. Both of them were visible during the same period of time.

Object details for NGC 772

Image details

RC 12"

ASA 12"