Constellations of the Month
by Rick Raasch
Scorpius is a large and sprawling constellation which lies near the Milky Way, and thus holds many bright open and globular star clusters: a welcome change after hunting down the faint and distant galaxies of the Virgo-Coma galaxy cluster. Both faint reflection nebulae and opaque dark nebulae also abound in this region, particularly in the region between Antares and Rho Ophiuci. This is due to the fact that we are looking in the direction close to the center of our galaxy. There are many gems in this area, and it is unfortunate for us that the observing season for this constellation is cut short both by the brief summer evenings, and by the constellation's southerly declination.
M-4 Lying about 1.5 degrees due west of Antares, this large globular cluster is both easily found, and a treat to observe. It is large, about 15' in diameter and is rather loosely concentrated, letting us resolve its individual stars rather easily. About 8-10 of its brightest members appear to form a bar right through its center, and gives the impression that the cluster is slightly elongated.
M-6 This is a fine open cluster just visible to the naked eye. It is sometimes called the Butterfly Cluster, as some observers see the shape of a flying insectoid amongst its stars. The cluster is large, about 25' in diameter, so use low powers to observe it. Over one hundred stars, many bright or relatively bright can be counted in this area.
M-7 One of the finest open clusters visible in the northern hemisphere, this object is best seen using binoculars or a finderscope. It is large, about 50' in diameter and contains many bright stars loosely concentrated at the center. Telescopic observers are awarded an added treat; at the western edge, but still within the cluster's boundaries, the faint globular cluster NGC 6453 can be seen. How many times have YOU observed M-7 without seeing this ghostly globular?
M-80 This is a small, tightly concentrated globular cluster which is difficult to resolve into its constituent stars, and then only around the edges. It is seen in binoculars as a fuzzy star.
NGC 6231 A fine open cluster, composed of over one hundred stars in a compact 15' area. It actually lies on another spiral arm of our galaxy, closer to the galactic center. According to Burnham's Celestial Handbook, if this cluster was at the same distance from us as the Pleiades, it would appear about the same size as that cluster, but would be about fifty times brighter, with its brightest members shining as bright as Sirius!
Next Month: The Cygnus Region
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