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Messier 83 NGC  5236
Imaged by Martin S. Ferlito
Gstar-EX Integrating Video Camera
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Discovered 1752 by Nicholas Louis de Lacaille.
Messier 83 (M83, NGC 5236) is one of the most conspicuous spiral galaxies in the sky. Situated in constellation Hydra, it is the southernmost galaxy in Messier's catalog.
M83 was discovered by Nicholas Louis de Lacaille at the Cape of Good Hope on February 23, 1752; it was his object Lacaille I.6. Thus it became the first galaxy to be discovered beyond the Local Group, and the third of all galaixes, after and M32. It was next cataloged by Charles Messier on February 17, 1781; from his mid-northern location in Paris (at 49 degrees Northern latitude), it is such a difficult object that he stated that: "One is only able with the greatest concentration to see it at all." The present author can confirm it is one of the most difficult Messier objects from South Germany. Due to this fact, older Northern-compiled catalogs tended to underestimate its brightness considerably; e.g., Becvar has it at a mere 10.1 mag only.
Early 19th century Australian observer James Dunlop has it as No. 628 in his catalog. Its spiral structure was noted and sketched by William Lassell who described it as a "three-branched spiral."
M83 was classified as intermediate between normal and barred spiral galaxies by G. de Vaucouleurs, in his classification this is SAB(s)c. It is magnificent in our image, has very well defined spiral arms and displays a very dynamic appearance, appealing by the red and blue knots tracing the arms. The red knots are apparently diffuse gaseous nebulae in which star formation is just taking place, and which are excited to shine by its very hot young stars. The blue regions represent young stellar populations which have formed shortly (i.e., some million or some dozens of million years ago). Between the pronounced spiral arms are regions with fewer stars. Dark dust lanes follow the spiral structure throughout the disk, and may be traced well into the central region to the nucleus, which has only 20" diameter. This nucleus shows strong emission lines. It is composed of an older yellowish stellar population which dominates the whole central region, and extends along the barlike structure.

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