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I am surprised it didn't happen. I think it's 1 star that goes supernova per galaxy every 100 years. Why didn't we see any yet? Reference: https://www.space.com

I am surprised it didn't happen. I think it's 1 star that goes supernova per galaxy every 100 years. Why didn't we see any yet? Reference: https://www.space.com/6638-supernova.html https://www.space.com/6638-supernova.html "On average, a supernova will occur about once every 50 years in a galaxy the size of the Milky Way" Why don't we see them with the naked eye?

ceejayoz 7y ago
> Why don't we see them with the naked eye? Same reason you can't read a book by looking at the binding. Most are obscured by gas, the galactic core, etc. as we view the galaxy edge-on. They also have to be fairly close to be visible to the naked eye. For example, https://en.wikipedia.org/wiki/SN_1987A https://en.wikipedia.org/wiki/SN_1987A was only about as far away as the other side of the Milky Way, and was perhaps barely visible in a dark sky at its peak magnitude.
cwbrandsma 7y ago
We don't see all of the Milky way as is, like the other side of the milky way is out of our view. https://www.universetoday.com/23173/the-milky-way-from-earth/ https://www.universetoday.com/23173/the-milky-way-from-earth... So that metric could be correct, but the supernova is outside of what we see.
Someone 7y ago
Let’s do some back-of-the-envelope reasoning. https://en.wikipedia.org/wiki/Supernova https://en.wikipedia.org/wiki/Supernova: ”The peak optical luminosity of a supernova can be comparable to that of an entire galaxy” There are over 2 trillion galaxies (https://en.wikipedia.org/wiki/Galaxy https://en.wikipedia.org/wiki/Galaxy), of which less than 10 (https://en.wikipedia.org/wiki/Galaxy#Distinction_from_other_nebulae https://en.wikipedia.org/wiki/Galaxy#Distinction_from_other_...) are visible with the naked eye. ⇒ ballpark, it seems only about one in 200 billion supernovae will be visible to the naked eye. Taking 1/50th supernova per galaxy per year, we get 4 billion supernovae per year, so we would expect to see one every 50 years, on average. Also, that can be as comparable may be fairly exceptional, the Milky Way may be above average size for a galaxy, or we just didn’t notice them (unless it were very bright, few people would notice a new ‘star’ showing up for a few days/weeks, and they may have been ‘behind’ other stars. That can easily happen for stars in the galactic plane of the Milky Way) Certainly, historically, we simply didn’t really look. It was not as if we had a world-wide scan for supernovae even 50 years ago (do we even have one today, or are we mostly discovering them by going through decades-old photos?)

ceejayoz 7y ago

> Why don't we see them with the naked eye? Same reason you can't read a book by looking at the binding. Most are obscured by gas, the galactic core, etc. as we view the galaxy edge-on. They also have to be fairly close to be visible to the naked eye. For example, https://en.wikipedia.org/wiki/SN_1987A https://en.wikipedia.org/wiki/SN_1987A was only about as far away as the other side of the Milky Way, and was perhaps barely visible in a dark sky at its peak magnitude.

cwbrandsma 7y ago

We don't see all of the Milky way as is, like the other side of the milky way is out of our view. https://www.universetoday.com/23173/the-milky-way-from-earth/ https://www.universetoday.com/23173/the-milky-way-from-earth... So that metric could be correct, but the supernova is outside of what we see.

Someone 7y ago

Let’s do some back-of-the-envelope reasoning. https://en.wikipedia.org/wiki/Supernova https://en.wikipedia.org/wiki/Supernova: ”The peak optical luminosity of a supernova can be comparable to that of an entire galaxy” There are over 2 trillion galaxies (https://en.wikipedia.org/wiki/Galaxy https://en.wikipedia.org/wiki/Galaxy), of which less than 10 (https://en.wikipedia.org/wiki/Galaxy#Distinction_from_other_nebulae https://en.wikipedia.org/wiki/Galaxy#Distinction_from_other_...) are visible with the naked eye. ⇒ ballpark, it seems only about one in 200 billion supernovae will be visible to the naked eye. Taking 1/50th supernova per galaxy per year, we get 4 billion supernovae per year, so we would expect to see one every 50 years, on average. Also, that can be as comparable may be fairly exceptional, the Milky Way may be above average size for a galaxy, or we just didn’t notice them (unless it were very bright, few people would notice a new ‘star’ showing up for a few days/weeks, and they may have been ‘behind’ other stars. That can easily happen for stars in the galactic plane of the Milky Way) Certainly, historically, we simply didn’t really look. It was not as if we had a world-wide scan for supernovae even 50 years ago (do we even have one today, or are we mostly discovering them by going through decades-old photos?)