Messier 101, also known as the Pinwheel Galaxy, is a large spiral galaxy located about 21 million light-years away in the constellation Ursa Major. It spans roughly 170,000 light-years across, making it significantly larger than the Milky Way. Seen face-on, its well-defined spiral arms are rich in gas, dust, and active star-forming regions, giving it a patchy, delicate appearance.