Re: dying suns

Some stars are so far away that by the time their light reaches us they may have already perished. And so it goes. I was wondering whether any of the major stars (i.e. belonging to constellations or likewise famous in the astronomy arena) have winked out in recorded memory? Or is it that for a star to die it would be so pale before hand as to be non-existent to your average star-gazer?

I seem to remember fiding out via Carl Sagan’s Cosmos TV series in the 80s that a star went supernova within human history - in the dark ages, IIRC. People could read by the light at night. Apparently, given the comparatively short time human beings have been keeping records, the incredibly long lifespan of stars, and the number of stars visible from our planet, the chances of this happening were astronomically (sorry) small.

This is all dim recollection, so I’ll leave it to the more expert dopers to give you a better answer.

Your probably thinking of the Chinese recording of a nova in 1054. Which they connected with the Crab nebula. There are supposed to be 90 such recordings of novas in Chinese records, the best and most reliable we have for these times.

None of them were probably known stars, but ones almost naked to the eye. My reasoning is that seeing a known star brighten and then disappear would be quite remarkeable, whereas the Chinese called them ‘guest stars’. And if it had happened I’m pretty sure that I would know about it.

But this is not because stars have to be dim to explode, rather that the vast majority of stars are too dim for us to see and novas are more likely to occur in that group then in the few bright ones.

Perhaps you want to know which visible star is most likely to wink out. I’d say the best bet, I would think, would be in Orion, both Betelgeuse and Rigel are pretty close.
Delta Scorpii in the constellation Scorpius is currently much brighter than normal. If it follows the same path as Gamma Cassiopeiae did back in the 1930’s, it’ll fade to near invisibility over the next few years.

Betelgeuse is very close to going (perhaps another millenium or so), and has probably already actually gone (we’re just waiting to see it). When it does, it’ll be the closest supernova in recorded history. I don’t think that any historical supernovae were visible to the naked eye before the fact, but that’s very difficult to determine.

This may be fudging some, but there do exist old photographic plates which show the progenitor star for SN 1987a. It wasn’t visible to the naked eye, though, and nobody paid it any attention until after the supernova.

Betelgeuse is very close. Only about 500 light years I think.

What effect will this have on earth when it finally goes nova?

The Bad Astronomer provided some excellent links on this very subject in a thread that was destroyed when the board imploded. Perhaps he could repost ?
The best estimate seems to be that not much happens if the supernova is over 30 lightyears away. That probably relies on our not being in the path of any major clumps or directed energy beams.
This NASA page has a discussion of the effects of a nearby supernova.

Thanks for the link, Squink.

There will be some effects, from the light if nothing else. Supernova Betelgeuse would be brighter than the full moon, which’ll probably confuse several species.

Here is a link to a page about risks from nearby supernovae. It’s pretty interesting.

There are lots of stars in the sky that will explode someday. Betegeuse, Rigel, Deneb… but they probably won’t go for another 100,000 years. Or they may blow tonight. The problem is, they are relatively close compared to their lifetimes.

There is a star called Sher 25 which looks a lot like the star that blew up to become Supernova 1987A. SN87A took about 40,000 years to blow once it became a blue supergiant, and Sher 25 already is a blue supergiant! It is actually a bit more massive and hotter than 87A’s star, so it’ll go in even less time. For my money, it’s one of a very few stars we know will explode in the next 30-40,000 years.

Here is a Hubble image of it. Sher 25 is the blue star centered in the ring of gas in the small square section in the center. You can read all about the Hubble image here. You can read about SN87A in a series of pages on my own website.

Just to clarify, the OP did not ask about supernovae per se. While a supernova is definitely the awesomest way for a star go to, the vast majority of them do not die in this manner.

Well, I would argue it does, indirectly. It mentions “famous” stars, which are the bright ones, and those tend to be massive, bright O and B stars (I note that Achernar is a Be star which too will blow up some day). A star like the Sun fades to invisibility past about 50 light years away.

Or at least several members of this species. :smiley:

Agreed that this is difficult to determine with certainty, but there’s evidence against the historically recorded supernovae bring previously visible stars. The Chinese records refer to “guest stars” (k’o-hsing), while the later European records are about nova stella. Neither term suggests a change in a previously observed star. Indeed, Tycho’s account of his first observation of the 1572 supernova explicitly mentions that nobody has previously recorded a star in the position where the “new star” is.

Furthermore, it’d be startlingly improbable for humans to either have recorded a visible star go supernova or to see such on a timescale of millennia. The usual estimate is that about there’s about 1 supernova (visible or not) in our Galaxy every 100 years. Since there’s less than 1000 naked-eye visible stars and about 100 billion stars in the Galaxy, it’s very improbable that any recorded supernova was a previously visible star. And if Betelgeuse does blow in the next 1000 years, then we’ll be extremely lucky.

One can extend a similar argument to star death in general. Say the average star’s lifetime is 1-10 billion years and something like 10-100 stars die in the Galaxy every year. But only 1 in 100 million stars in the Galaxy are visible to the naked eye, so it’s very unlikely that such a death has ever been conciously observed.

Just to be pedantic, the only supernova ever seen with a positively identified progenitor star is Supernova 1987A. It wasn’t until the supernova faded somewhat before the progentor was known for sure as Sanduleak -69 202. There was another bright star a few arcseconds away (in the Hubble images, it’s the bright star superimposed over the upper ring).

Betelgeuse may take several tens of thousands of years before it explodes. Or it may go tonight. Since it is only 400 light years away, it would have had to explode in the past 400 years for it to be gone “now”. Given that, the odds are IMO low for it to be gone already. That was my point before; you want a star that is far away relative to the amount of time it has left.

Well, one of my undergraduate professors studied Big B, and he always talked in terms of “We’ll see it go within a thousand years or so”. I haven’t checked any of his calculations on that, but I take his word on it.

While that’s more or less true, you’re not taking everything you need to into account. There’s also a selection effect that The Bad Astronomer mentioned - a disprportionately high number of visible stars are supernova progenitors.

But regarding that point, I just wanted to note that while the OP is probably very interested in hearing about supernovae, they would probably also be interested in hearing about any kind of stellar star death that we know about. I know that not every visible star in the sky is type O or B (although the only one I can think of offhand is Vega - I’m not an observationalist).