M83 June 25, 2010 - M83 - Southern Pinwheel Galaxy This image from the Wide-field Infrared Survey Explorer (WISE) is of the nearby galaxy Messier 83, or M83 for short. It is a spiral galaxy approximately 15 million light-years away in the constellation Hydra. It is sometimes referred to as the southern Pinwheel galaxy. M101 is called the Pinwheel galaxy and M83 has a similar appearance, but it is located in the southern sky. At about 55,500 light-years across it is a bit more than half the size of the Milky Way Galaxy, but it has a similar overall structure. Like the Milky Way, most of M83’s stars, dust, and gas lie in a thin disk decorated with grand spiral arms. We see the disk of M83 nearly face-on (whereas we see the disk of the Milky Way edge-on since we are inside it). The spiral arms are places where the disk is a little denser with stars and gas, which leads to a higher rate of star formation in them. Where there is star formation, we find more very bright, short-lived stars, and plenty of dust (green and red in this infrared image). M83 also has a central bulge of stars and dust that has a component that is roughly spherical and a component that is shaped like a bar. So M83 is referred to as a barred spiral galaxy. This image was made from observations by all four infrared detectors aboard WISE. Blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is primarily light from stars. Green and red represent light at 12 and 22 microns, which is primarily emission from warm dust. Image Credit: NASA/JPL-Caltech/WISE Team