The Pinwheel Galaxy (Szélkerék in Hungarian) is one of the last entries in the Messier catalog, discovered by Pierre Méchain in 1781. It has a grand-design pattern, meaning nothing more than that the spiral arms are prominent and well-defined. Also known as NGC 5457, the galaxy lies at 21 Mly. According to this paper, it has a mass of 9.8×1010 solar masses, way less than the Milky Way’s ~1012 solar masses, see this paper.
As a sidenote, our home is actually one of the most massive galaxies in the wider neighborhood, the exact value depending on the study, placing us somewhere a bit below down to at about half of M31 Andromeda’s mass, which is just heavy compared to the other spirals on the sky. As another sidenote, it is hard to find the masses of galaxies on the internet. As one more sidenote, it is tricky to find out distances of galaxies in scientific catalogs not meant for the general public, thus not containing a trivia section.
Besides M101, the other prominent object in the frame is NGC 5474, a peculiar dwarf galaxy showing some reminiscent spiral structure with an offset core. It may be classified as a dwarf spiral galaxy, a relatively rare group of dwarf galaxies. Easily seen objects on the picture:
- M 101, NGC 5457 [galaxy in UMa] Pinwheel Galaxy, Szélkerék-galaxis 7.5m [wiki], at ~21 Mly
- NGC 5474 [galaxy in UMa] 11m [wiki], at ~21 Mly
- NGC 5477 [galaxy in UMa] 14m [wiki] (the patch near M101, at ~20 Mly)
- PGC 49919 [galaxy in UMa] 14.87m [simbad]
- PGC 50581, UGC 09071 [galaxy in UMa] 14.93m [simbad]
- PGC 50505 [galaxy in UMa] 15.44m [simbad]
- PGC 50438 [galaxy in UMa] 15.69m [simbad]
- PGC 2464645 [galaxy in UMa] 16.18m [simbad]
- PGC 2468609 [galaxy in UMa] 16.32m [simbad]
I find it amasing that objects as faint as 16m show up on this, not so deep picture.
I used my modded Canon 1100D on the N 157/750 scope, field corrected by Baader MPCC Mark III, with the HEQ5 mount. 19x90sec, ISO 3200. Platesolving done with astrometry.net.