M-83
This is one of the finest examples of a face on barred spiral galaxy in the sky, and is sometimes called the "Southern Pinwheel". It is large, about 10' in diameter, with an obvious central bar and spiral arms which seem to go all the way around the galaxy. Often photographed by amateurs, this is a real gem of the night sky.
M83 was discovered by Abbe Nicholas Louis de la Caille at the Cape of Good Hope in 1751-52. It has very well defined spiral arms and displays a very dynamic appearance, appealing because of 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 recently (i.e., some million or some dozens of million years ago). The dust lanes may be traced well into the central region to the nucleus, which has only 20" diameter.
For years, M83 had been the galaxy with most discovered supernovae, but recently NGC 6946 came up with the same number of 6, or even one more if 1945B should be an error.