M101 – The Pinwheel Galaxy – is a face-on spiral galaxy 21 million light-years away from Earth in the constellation Ursa Major (Big Dipper). Located just west of the last star in the handle.
M101 is a large galaxy containing approx 1 trillion stars, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of between 100,000 and 120,000 light-years.
M101 has a high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1,264 H II regions were cataloged in the galaxy. Three are prominent enough to receive New General Catalogue numbers—NGC 5461, NGC 5462, and NGC 5471.
There are at least 4 different galaxies resolved within this image. M101 is the largest and closest. NGC5474 is at the lower left. NGC5477 is above the bottom arm of M101 and appears equally distant between the two yellow stars. NGC5473 is at the far left of the image in the middle.
Image acquisition via APT using a SW Esprit120ED, ASI2600MC Pro, OPT L-Pro filter, & EQ6r Pro mount from my backyard in the hills of western NC.
397 300s subs for an exposure of 33 hours.
