This supernova was discovered on 2022-04-16 by Koichi Itagaki. It is of type Ia, meaning it originates from an exploding white dwarf in a binary pair. I photographed it during two consecutive nights. The time of year means there was a limited amount of astro darkness.
The supernova is located in the galaxy NGC 4647 near the more wellknown M60. The host galaxy is at a distance of 63 million light years. So what we see now happened a very long time ago.
The particular type of white dwarf star that causes a type Ia supernova has physical properties that means it has an upper mass limit. The limit is called the Chandrasekhar mass and is about 1.44 solar masses. If the star exceeds this mass limit it will explode as a supernova.
But why would a star increase in mass and eventually reach the mass limit at some point?
It is assumed that this kind of event occurs if the white dwarf star is part of a binary pair, and the white dwarf slowly acquires materia from it’s companion in the binary pair, and so eventually reaches the Chandrasekhar mass and explodes. This has some interesting consequenses. Since this type of supernova explodes at a well known mass, all such supernovas reach essentially the same absolute luminosity. This, in turn, means that it is possible to calculate the distance to the supernova. Also, the time schedule of these supernovas can be estimated rather well with calculations. The time from the explosion to maximum luminosity is known to be around 17-18 days, and when the maximum point in the luminosity curve is reached, we can calculate backwards and determine when the star exploded.
Below is a zoomed out image.
