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messier 45

 

Known to most as the Pleiades, M 45 is a brilliant example of an open star cluster. The bright gouping contains more than 300 stars in total, though only about a dozen are visible to the unaided eye. Even more striking than the cluster, however, is the delicate cirrus-like structure of the surrounding reflection nebulosity. Despite first impressions, this dusty nebula is not directly associated with the birth of the star cluster itself. Rather, the cluster members are apparently traveling through a nearby cloud of gas and dust known as IREC 245. The relatively fast motion of the stars combined with their unusually high rotational velocities creates intense magnetic fields within the cloud. Such magnetic fields are responsible for the many thin filaments and peculiar striations seen throughout the nebulosity. As with most reflection nebulae, the striking blue coloration is not only due to the color of the nearby starlight, but also etermined by the size of the dust grains doing the "reflecting". Most interstellar dust is composed of particles much smaller than the wavelengths of red and green light, they therefore reflect blue light with much more efficiency. If viewed in a dark room, this image actually shows much of the surrounding molecular cloud extending quite far from the heart of the cluster. Also of note is the tiny edge-on spiral galaxy UGC 2838 located near the image's righthand border. Image taken with homemade 8-inch f/5.4 astrograph and SBIG STL-11000M. LRGB image composed of 30 minutes each R,G,B and synthetic L channel. Click on the image above for the high resolution version.