M 101 with NGC 5474

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.