Discovering Supernovae

Astronomers find supernovae by comparing two or more images of the same region in the sky and looking for sudden changes in the brightness of an object in the images. Since supernovae are found in galaxies, we search for supernovae by comparing images of the same galaxy taken at different times. Once astronomers find a supernova, they take as many images as possible over a period of months to study how the supernova changes in brightness. Rubin Observatory takes images of the entire sky (visible from its location) every three to four nights, so it has a much greater ability to detect the changes in brightness of objects than other telescopes.

a large face on spiral galaxy shows the supernova near the end of one of its spiral arms, which contain many red clouds of star forming regains and dark dust lanes. — SN 2023ixf shines brightly in one of the arms of M101, the Pinwheel Galaxy. Data from International Gemini Observatory/NOIRLab/NSF/AURA Credit: J. Miller (Gemini Observatory/NSF’s NOIRLab), M. Rodriguez (Gemini Observatory/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab). Astronomical processing done with DRAGONS 3.1.

This image shows a supernova that exploded in the nearby Pinwheel Galaxy, M101. The supernova is circled. Notice that it is bright compared to the light from its host galaxy. But how can we know if it’s a supernova? The answer is, with this picture alone, we can’t!