A bright supernova in NGC 7331

NGC 7331 is a spiral galaxy in the constellation Pegasus. This galaxy makes a popular astrophotography target, often imaged in the same field of view along with Stephan’s Quintet. On 14 July 2025, a supernova, named SN 2025rbs, was discovered in this galaxy. At the time of discovery, it was shining at about magnitude 17, but has since brightened up to 13 at the time of writing this post.

SN 2025rbs is a type Ia supernova: this type of supernovas typically takes place in binary star systems, in which one of the components is a white dwarf. The white dwarf receives a flux of matter from a more massive companion star, creating an accretion disk which collapses and eventually ends up in a supernova explosion.

I imaged the galaxy and the supernova from Valle d’Aosta (Italy) on the night of 21-22 July 2025 through a 10-inch RC scope and a Toutek 2600M CMOS camera. Total exposure time was about 3 hours in the L channel only. Below are three photos:

1. An image of NGC 7331, showing the supernova near its nucleus, engulfed in the nucleus's bright glare;
2. The same image of NGC 7331, annotated to bring out the nearby galaxies (NGC 7335, 7336, 7737 and 7340);
3. A higher magnification close-up, where the supernova is marked by an arrow.

Enjoy! :-)