NGC 6946 is a galaxy in Cepheus and is also known as the Fireworks Galaxy. Its called the Fireworks Galaxy because it has a record number of observed supernova in it.
And this image is no exception. The supernova SN2017eaw appears in this photograph.
In May of 2017 I took delivery of a new mount, a 10Micron HPS GM1000. This is a very nice mount indeed and I wanted it for mobile, high precision imaging. Once I received the mount, I needed to do testing and learning. For this, I decided to use the TeleVue NP101is and reducer since it produced a very wide field, is lightweight and is really easy on the mount. The idea being to get the mount running with known gear that would not introduce any problems while I went through the initial commissioning process.
It just so happened that NGC 6946 galaxy and the cluster NGC 6939 were in a good position so I used them as a test target. Not a bad choice since I had stars, a cluster and a galaxy all in the same field. Little did I know that three days later a supernova would go off in that galaxy.
So the supernova did occur on or about May 14, 2017. But I didn't learn about it until nearly two weeks later when I spotted a post in a popular forum (Cloudy Nights). It seems that a gent who is more on the ball than I learned about the supernova and imaged it a few days after. He also had in his photo archives an old photo of the galaxy he took long before the supernova went off. Using thes two photos he did a very good post showing the before and after images.
Once I saw that post, I realized I had a really lucky image here and added a post of my own showing a crop of the galaxy a mere three nights or so before the discovery. It did indeed show there was no supernova at that point. Then I followed up and took another image that showed the new supernova.
These three images show the before, after and located supernova:
May 10, 2017,
About 3 days before the supernova
May 27, 2017,
About 14 days after the supernova
And this image indicates which "star" is the supernova.
Indeed, not really that spectacular but consider, it's in another galaxy so its really, and I mean really far away yet from here it looks as bright as any star in our own galaxy. So from close up… wow!
And so what is a supernova anyway you might ask? Well, it’s a star that has reached the end of its life, which caused it to collapse on itself then explode. This page is too short to go into all the physics involved in the death of a star and the resulting supernova but I will add that this only happens to a small fraction of stars and they need to be very huge (as compared to our sun anyway).
Lastly, in case you missed the top of this article, you might ask, why is this galaxy called the Fireworks Galaxy anyway? Well, it has a record number of observed supernove in it and as we can see, they go off like fireworks.