M33 - Triangulum Galaxy
A member of our Local Group at 3 Mly distant, Triangulum is the runt in the family of regular galaxies at 60,000 ly in diameter. It is also a curious spiral in that it lacks a central bulge and supermassive black hole, making it a focus of study for galaxy formation and particularly the role of these black holes in galactic evolution. Triangulum presents itself nearly face on with several moderately defined, delicate and punctate spiral arms. Capture of Ha (red) reveals a host of swirling energized stellar nurseries that decorate the spiral arms out to the very edges of the galactic disk. Some of these patterns are rich with structure even at this distance and image scale owing to their great size, many hundreds or thousands of light years wide. The most prominent of these, featured in the upper right of the galaxy is NGC 604, one of the largest sites of stellar formation yet discovered at 1500 ly wide and harboring hundreds of stellar hyper giants. That's 40 times the size of our Orion Nebula with a luminosity over 6000 times greater!