Spotting a Supernova in NGC 5806

This image shows NGC 5806, a spiral galaxy in the constellation Virgo. Also visible in this image is the afterglow of a supernova explosion called SN 2004dg. The fading light from this outburst, caused by a giant star exploding at the end of its life, can be seen as a faint, yellowish dot near the bottom of the galaxy. High-resolution images of NGC 5806 predating SN 2004dg were present in the Hubble data archive, so a rare and important before-and-after image comparison was possible. While the supernova’s progenitor could not be positively identified, it is suspected to be a relatively low-mass, low-luminosity red supergiant. Aside from the supernova, NGC 5806 is a relatively unremarkable galaxy. The galaxy’s bulge (the densest part in the center of the spiral arms) is a so-called disk-type bulge, in which the spiral structure extends to the center of the galaxy.