If you’re asking whether any supernova have occurred, then yes, they have.
If you’re asking whether humans have seen a supernova, then yes also - the most famous is probably SN 1006, which was the brightest stellar object ever seen by humans, brighter than venus in the sky, and was recorded in the year 1006 by many different societies. There have been several others documented over the last 1000 years.
In addition, which might be more what you’re asking, there have been stars, or at least light sources that look like stars, which have simply appeared and vanished again within a matter of minutes or hours, and their disappearances are often left poorly explained - they could be supernova that for some reason didn’t go nova, or something else entirely. There’s a project called VASCO (Vanishing and Appearing Sources during a Century of Observation):
I get the definition and extrapolation, but I was wondering if any observable phenomena has occurred. Thanks.
If you’re asking whether any supernova have occurred, then yes, they have.
If you’re asking whether humans have seen a supernova, then yes also - the most famous is probably SN 1006, which was the brightest stellar object ever seen by humans, brighter than venus in the sky, and was recorded in the year 1006 by many different societies. There have been several others documented over the last 1000 years.
In addition, which might be more what you’re asking, there have been stars, or at least light sources that look like stars, which have simply appeared and vanished again within a matter of minutes or hours, and their disappearances are often left poorly explained - they could be supernova that for some reason didn’t go nova, or something else entirely. There’s a project called VASCO (Vanishing and Appearing Sources during a Century of Observation):
https://www.iflscience.com/disappearing-stars-in-the-1950s-associated-with-uaps-and-nuclear-weapons-tests-
https://www.smithsonianmag.com/air-space-magazine/stellar-mystery-how-could-100-stars-just-vanish-180973821/