M83 (NGC 5236) (The Southern Pinwheel)
Distance: 14.7 Million Light Years

Right Ascension: 13 : 37.0 (hours : minutes)
Declination: -29 : 52 (degrees : minutes)


text copyright Robert Gendler 2008

M83 is a nearby face-on barred spiral with a classic grand design form. It is the principle member of a small galactic group including NGC 5253 and about 9 dwarf galaxies. M83 has been a prolific producer of supernovae, with six observed in the past century, second only to NGC 6946 which has produced a record 8 supernovae. The high SN rate is indicative of an exceptionally high rate of star formation coinciding with its classification as a starburst galaxy, similar to M82 and NGC 253. Despite its symmetric appearance, the central 1000 light years of the galaxy shows an unusually high level of complexity, containing both a double nucleus and a double circumnuclear starburst ring. High resolution observations at radio wavelengths show the visible nucleus to be curiously offset from the true dynamical nucleus by some 200 light years. A gaseous accretion disk was found with a diameter of almost 400 light years rotating at high velocity (180 kilometers per second) around the galaxy's off centered nucleus. The nature of the double nucleus is uncertain but some evidence suggests that the origin of the off centered nucleus may be a remnant core of a small galaxy that merged with M83 in its distant past. Supporting this theory is other evidence (a 100,000 light year stellar arc) that M83 recently cannibalized a small satellite galaxy. Other examples of double nuclei include galaxies such ARP 220 which has acquired a second nucleus through the violent merger of a satellite galaxy. The other well known galaxy with a double nucleus is M31, but its origin is almost certainly explained by a different mechanism (see M31 core).

As a starburst galaxy M83 shows a bright nuclear region particularly in the infrared.
The star clusters in the nuclear starburst rings are located between 160 and 400 light years from the galactic center and are mostly young stars between 5 and 10 million years old indicating very recent activity with the rings. The central nuclear starburst activity is almost certainly driven by bar induced gas accumulation in the center of M83 (see M94 and NGC 4725) and has been further shaped by the dynamics of the double nucleus. Recently a 1500 light year sized subsystem of rotating stars similar to Gould's belt in the Milky Way, has been identified in M83 (see Milky Way).