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Messier 101

 

Spanning nearly the same amount of sky as the full moon, the Pinwheel Galaxy (M 101) is one of the most remarkable examples of a face-on spiral galaxy in all the heavens. Though discovered by French astronomer Pierre Mechain in 1781, it wasn't until the mid 19th century that the "spiral" nature of M 101 was revelaed by the monstrous telescopes of Lord Rosse. Besides having one of the largest spiral discs of any known galaxy, M 101 also happens to be relatively close which allows many of its features to be resolved by earthbound telescopes. Amongst these features are some 1264 individual "knots" of emission nebulosity, ten of which are obvious enough to have their very own designations in the ubiquitous NGC catalogue! A large number of these regions can easily be spotted in the image above as tiny pink knots scattered along the winding blue arms of hot young stars. As with other typical spiral galaxies, the central bulge of the Pinwheel appears yellowish in color due to the concentration of older population II stars in that area. More on the subject of galaxy coloration can be found by clicking here. The image above is somewhat of a panoramic view of M 101 and its surroundings and includes several other interesting galaxies, including the rather bizarre NGC 5474 located to the far left. Recent research shows that this galaxy actually shares an extended envelope of molecular hydrogen with M 101, and it appears that a large portion of the NGC 5474's gas along with its nucleus have been dislodged from its central disc due to tidal effects. Other galaxies in the field include another of the Pinwheels distorted companions NGC 5477 located near the top of the image and NGC's 5473 and 5422 (the tiny spindle), both loctaed to the right of M 101 in this shot. Please click on the above image for higher resolution. Image taken with homemade 8-inch f/5.4 astrograph and SBIG STL11000M using 110 minutes of luminance and 30 minutes each of R, G, & B.