This has just happened today! Me and my Dad had set up out 14 inch Dob and observed the galaxy on Monday, and there was certainly no star there. The supernova is 12th magnitude and brightening. This means it’s well within the range of amateur telescopes, a 4 inch should have no problem seeing it, weather permitting of course.
Looking at supernovas is looking into the past, and this particular star exploded about 11.5 million years ago. That’s how it is when you look at any distant object in the night sky. For example, whenever you look up at the moon, your actually seeing how it appeared just over a second ago. That supernova is 11,420,000 light years away, so it had to travel that distance. The light traveled all that way and took so long to get here. That star is long gone and likely has formed a planetary nebula of some sort.
The galaxy M82 itself is an interesting object. It is an edge on spiral galaxy, often called the Cigar Galaxy because of its appearance. It is also designated as NGC 3034. Through most telescopes it looks like a pale elongated smudge, and light and dark areas and rifts can be seen throughout, as seem in photographs. M82 is a very active galaxy, with a bright “starburst” region, further information here
I’m setting up the RV-6 this evening to take a peek at it, should provide a great view of it, I’ll most likely make a sketch of it now, and maybe later too and compare the brightness of it. Go on out and take a look!