The description you shared of Messier 101 (the Pinwheel Galaxy) is spot-on and captures what makes this one of the most stunning and intriguing spiral galaxies in the northern sky. It's a classic grand-design spiral, appearing nearly face-on to us, which gives astronomers (and astrophotographers) an incredible view of its sweeping arms, star-forming regions, and overall structure.Your key points align well with current astronomical data:Location and distance: In Ursa Major, roughly 21–25 million light-years away (estimates vary slightly depending on the method, but ~21–25 Mly is the consensus range). Size: Diameter around 170,000 light-years—indeed about twice that of the Milky Way. Star count: Roughly a trillion stars, making it exceptionally massive and luminous for a spiral. Appearance and features: Face-on orientation reveals the prominent spiral arms, abundant gas and dust, and thousands of H II regions (those glowing nurseries of massive, hot young stars are a highlight—some of the brightest ones even have their own NGC designations). Central black hole situation: This is one of the more interesting quirks. Many sources (including detailed studies from radio and X-ray observations) indicate no clear evidence for a supermassive black hole (SMBH) at the center—no strong central emission source typical of an active galactic nucleus (AGN). Instead, the galaxy shows multiple X-ray point sources, likely from stellar-mass black holes in binary systems or other high-energy phenomena. Some older or less precise sources occasionally claim a small SMBH (e.g., a few million solar masses), but more reliable references lean toward it being absent or extremely under-massive/undetectable compared to most large spirals. This makes M101 somewhat unusual among big galaxies. The Pinwheel's asymmetry (its core is slightly offset, and the arms look lopsided in deeper images) is thought to result from past gravitational interactions with companion galaxies in the M101 Group.Tony Hallas is a renowned astrophotographer known for his breathtaking wide-field and deep exposures of nebulae and galaxies—his image of M101 likely highlights those delicate outer arms and the galaxy's overall ethereal glow beautifully.If you're sharing this as a favorite or want to dive deeper (e.g., into specific Hubble/Chandra composites, recent star-formation studies, or how to observe it yourself), let me know! It's always a rewarding target in spring skies under dark conditions.