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I heard about the 1054 supernova that was visible with the naked eye.

Of course, these events happen at random. But just like with radioactive decay, it must be possible to determine statistics on these kinds of events.
Wikipedia says

The total supernova rate in our galaxy is estimated to be between 2 and 12 per century

but this doesn't indicate anything about their visibility from Earth. In fact, quite a few supernovas in the Milky Way probably go unnoticed, so the rate of visible supernovas is likely lower.

In addition, type Ia supernovas can outshine the galaxy they are in, so if one occurred in Andromeda or a Magellanic Cloud, it might be visible. So there possibly could be more visible supernovas than there are supernovas in just our Galaxy.

What is the average time between two supernovas that are visible with the naked eye?

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    $\begingroup$ supernova sn1987a in the Large Magellanic Cloud was visible to the naked eye. Indeed the first detection of it was made that way. $\endgroup$ – Steve Linton May 14 '20 at 15:10
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    $\begingroup$ I have asked astronomy.stackexchange.com/questions/36167/… which addresses a specific part of this issue. $\endgroup$ – Steve Linton May 14 '20 at 16:03
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One way to answer this is to look at how often naked-eye supernovae were seen in the past. In the last 2000 years, there have been (at least) eight such supernovae recorded: in 185, 393, 1006, 1054, 1181, 1572, 1604, and 1987. Seven of these were in our galaxy, while the last (SN 1987A) was in the Large Magellanic Cloud.

It's possible that supernovae in the far southern sky would not have been visible to Chinese astronomers (the most reliable and comprehensive records we have), so some additional supernovae visible from the far south may have been missed. We could round the total up to ten, which gives us a rate of about one every 200 years. If you want to worry about some being visible but not recorded (e.g., because they happened during a particularly chaotic time in China), then perhaps the rate would be a little higher -- maybe one every 150 years?

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  • $\begingroup$ SN1885a reached magnitude 5.85 which might just be naked eye visible under ideal conditions. $\endgroup$ – Steve Linton Nov 8 '20 at 17:36
  • $\begingroup$ @SteveLinton True, but would it have been noticed in an earlier era? I was taking the example of SN 1054 as suggesting "bright enough to be noticed by historical observers". (There may well have been more "barely visible" SNe, but it's hard to estimate how many...) $\endgroup$ – Peter Erwin Nov 8 '20 at 21:22
  • $\begingroup$ Historical observers knew the naked eye skies extremely well and many of them had the benefit of much darker skies. I guess 1885 might be a bit too late in the sense that by then any keen observer had a telescope. Anyway I don't know if its recorded anywhere. $\endgroup$ – Steve Linton Nov 8 '20 at 23:41
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This event is very rare and occurs every few 100 years in our galaxy, which makes it unsure if you could even see 1 in your lifespan. you can see how it would look from Earth and read a little about such events here. Also, there is going to be another supernovae probably visible from naked eye in 2022, which the above link is talking about. Since such a supernovae happens so rarely, that I wasn't even able to find a single image of one, perhaps one happened most recently in the 1600's. This link talks about how you could locate the 2022 supernovae. Hope this helps.

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  • $\begingroup$ Your link is to a description of a classical nova, not a supernova. $\endgroup$ – Peter Erwin Nov 6 '20 at 17:25
  • $\begingroup$ I am sorry I didn't observe that, my fault, now I have changed my link, I hope it should be fine. $\endgroup$ – RyugaGod Nov 8 '20 at 9:09

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