M74, spiral galaxy in Pisces

Image by Danny Flippo
Pierre Méchain found M74 at the end of September 1780. He reported his discovery to his friend, Charles Messier, who determined its position and included it in his catalog on October 18, 1780. It is among the first "Spiral Nebulae" recognized; Lord Rosse lists it as one of 14 "spiral or curvilinear nebulae" discovered before 1850.

This conspicuous spiral is a prototype of a grand-design Sc galaxy. It is classified in more detail in De Vaucouleur's scheme as of type SA(s)c, i.e. a barless (therefore "SA") Sc spiral without a ring structure ("s"). Its distance may be about 30 to 40 million light years (R. Brent Tully's Nearby Galaxies Catalog has 32), as it recedes with 793 km/sec. Then its spiral arms are about 1000 light years broad. They are traced with clusters of blue young stars and pinkish colored diffuse gaseous nebulae (H II regions) in color photos, and reach out to cover a region of more than 10 minutes of arc in diameter, corresponding to roughly 95,000 light years, or about the same size as our Milky Way galaxy. The Webb Society Deep-Sky Observer's Handbook gives a number of 193 known H II regions. The nucleus of Sc spiral galaxy M74 is small and bright