How many known stars has disappeared from sight for no known natural reasons, if any?

[statickid]

I'd say the "rarity" is only based on the sample size. SOMEWHERE in the universe, there is a star supernova-ing right now...somewhere.... :lol:

 

[RisingFury]

I was looking at the night-sky a few days ago when I came to think about this. All the known star-signs are still there (that covers at-least a few thousand years of human history), all the stars used for navigation throughout relatively modern times are still there (that's at-least 500 years of human history), and that just made me wonder if there are any examples at all of known stars that were once observed but can't be today (and in extension of that I came to think of black-holes)

My own personal quick first-hand evaluation of this was to simply count how many stars I have seen myself through time that I can't locate anymore, which is zero. All stars I can recognize are still there, thus zero is missing. Rough and basic, certainly, but the most direct observation of the night-sky none-the-less

Star signs won't degrate because the stars will eventually die. They will degrade because the stars are moving. Every star has it's own velocity around the galactic center, so relatively to the Sun those velocities are in the range of a few 10 km/s.

There were a few stars visible from Earth that went nova, got brighter for a few weeks, then disappeared completelly. The two most prominent that I can think of are these two:
[ame="http://en.wikipedia.org/wiki/SN_1054"]SN 1054 - Wikipedia, the free encyclopedia[/ame]
[ame="http://en.wikipedia.org/wiki/SN_1604"]SN 1604 - Wikipedia, the free encyclopedia[/ame]

These two became very bright.

 

[JEL]

Star signs won't degrate because the stars will eventually die. They will degrade because the stars are moving. Every star has it's own velocity around the galactic center, so relatively to the Sun those velocities are in the range of a few 10 km/s.

There were a few stars visible from Earth that went nova, got brighter for a few weeks, then disappeared completelly. The two most prominent that I can think of are these two:
SN 1054 - Wikipedia, the free encyclopedia
SN 1604 - Wikipedia, the free encyclopedia

These two became very bright.

Thanks for that info, very interesting actually, but let me just re-iterate the original question by quoting my first post:

How many observed/confirmed stars has disappeared from sight for no known natural reason, if any?

Stars which, based on the current mainstream understanding of how they should evolve, should still be there, but aren't.

Stars that behave in explainable ways, such as those 2 you describe, does not fall into the category I'm after in this thread. But thanks for the links anyway though




The reason I mentioned star-signs is because they are probably the safest way to reference earlier astronomic observations, which would increase the time-span of useful observation.

A very faint star _could_ have been spotted a long time ago (several thousand years perhaps) and be missing today, but if the star is only referenced as, for example, the Bethlehem star, then we can't deduce any real useful info from that. We don't know with any high probability what star the Bethlehem star actually is/was, only that there is talk about it having been seen around year zero.

However, if the North star could not be seen today we would be pretty certain it was once there simply because many references of it are very clear and hard to mistake for other stars.
And if it did not show any signs of having gone nova before disappearing, then that would be the kind of star I'm asking about in this thread
So far I'm still at zero such stars.

 

[RisingFury]

Stars that behave in explainable ways, such as those 2 you describe, does not fall into the category I'm after in this thread. But thanks for the links anyway though

Stars don't just go poof and disappear. If a star has 1 solar mass of material, there will still be roughly that amount in the area. Some mass is usually consumed by the fusion, but material is always left over...

If a star were to collapse into a black hole a few thousand years ago, it wouldn't suck in all gas. The remenatns would still be visible today. The crab nebula, as a result of SN 1054 has a neutron star in the middle...

If there's a bright star seen in the sky, then it's reasonably close to Earth and even if it exploded the remenants would be seen today...

The reason I mentioned star-signs is because they are probably the safest way to reference earlier astronomic observations, which would increase the time-span of useful observation.

You need to take into account that stars move around and that earlier civilisations might have seen different shapes in same star patterns, or they could have seen same shapes in different patterns.

A very faint star _could_ have been spotted a long time ago (several thousand years perhaps) and be missing today, but if the star is only referenced as, for example, the Bethlehem star, then we can't deduce any real useful info from that. We don't know with any high probability what star the Bethlehem star actually is/was, only that there is talk about it having been seen around year zero.

Whatever the early civilisations saw, we can see now with ease. We have telescopes that allow us access to the universe that would leave the early skywatching civilizations in awe.

Another explanation for the Bethlehem star is that it might be Jupiter and Saturn very close together - within less then a degree. That happens every 20 or so years. One such occurance is in October of "year -6" and another in December of year 14. Might also be Venus and Jupiter, but not sure if they'd appear in the "correct" part of the sky.

However, if the North star could not be seen today we would be pretty certain it was once there simply because many references of it are very clear and hard to mistake for other stars.
And if it did not show any signs of having gone nova before disappearing, then that would be the kind of star I'm asking about in this thread
So far I'm still at zero such stars.

There are many references of dragons in various civilisations that never had any contact. Does that mean that dragons were real, even though we can't find them today?


Stars don't just go poof and vanish into pitch black. There's always stuff left behind, at least in a timeframe as short as we're talking about...

Material glows after the star dies because it's ionized, so you can clearly see it with a telescope...

 

[JEL]

Stars don't just go poof and disappear.

Apparently they don't, hence the number zero

If a star has 1 solar mass of material, there will still be roughly that amount in the area. Some mass is usually consumed by the fusion, but material is always left over...

I'm not looking for mere mass/matter, but for stars that are no-longer observable even though they should be according to current models. The mass/matter may still be there, that's irrelevant. What matters is (pardon the pun) that the observable star is no-longer observable even though it should be. If SUCH a star was discovered, and at the moment none have been (zero), then THAT would be the one I'm interested in. The anomaly, you might say, the one that strays from the established norm, of which there are none known at this time.

So I'm not really disagreeing with you, I was just looking to see if there WAS indeed any known star that had exhibited that odd behavior

Looking for anomalies can produce 2 results; either some are found and current theories can be refined, or none is found and current theories are left un-changed (or may even be considered re-enforced by the lack of such anomalies)

If a star were to collapse into a black hole a few thousand years ago, it wouldn't suck in all gas. The remenatns would still be visible today. The crab nebula, as a result of SN 1054 has a neutron star in the middle...

Are you suggesting that if a star collide with a black-hole that a supernova would then always be the result of such collision?
That does not appear to be what current mainstream theories believe according to the wiki-page: [ame="http://en.wikipedia.org/wiki/Supernova"]Supernova - Wikipedia, the free encyclopedia[/ame]

SN 1054 is called a core-collapse supernova, on the wiki-page, and there are no suggestions of any collisions being the cause for the core-collapse.
So apparently this star followed the current established mainstream rules for star-behavior, so to speak, and thus didn't do anything un-natural.

You need to take into account that stars move around and that earlier civilisations might have seen different shapes in same star patterns, or they could have seen same shapes in different patterns.

The Zodiac starsign apparently dates back to around year -1000 (1000 BC), so that's at-least 3000 years we can go back without ending up in complete randomness.
The shorter we go back, the more precise we can be of-course, so even here I don't disagree with you

Whatever the early civilisations saw, we can see now with ease. We have telescopes that allow us access to the universe that would leave the early skywatching civilizations in awe.

Any star they could see, that is still visible, we can see to. I agree with you on that.

But for exactly the reason you point out, earlier limitations in observing capabilities relative to present-days, we are limited to using only the stars we can be relatively sure are identified the same by them and us. We can't use our own recent discoveries in a historic context, since they are exactly that; recent discoveries. But Polaris is a long-known star, 2000 years of history, and well-known, and thus is the type of star we can be pretty sure is identified the same by both them and us (It was easy enough to observe distinctively even back then)

Incidentally, I just read this about Polaris:

Recent research reported in Science suggests that Polaris is 2.5 times brighter today than when Ptolemy observed it, changing from third to its current second magnitude. Astronomer Edward Guinan considers this to be a remarkable rate of change and is on record as saying that "If they are real, these changes are 100 times larger than [those] predicted by current theories of stellar evolution."

Link: [ame="http://en.wikipedia.org/wiki/Polaris"]Polaris - Wikipedia, the free encyclopedia[/ame]
Not exactly what I was looking for, since it's not missing, but since it may be an anomaly it's in the same ball-park. Another possible opportunity to learn something further, maybe
I've got to thank you for that actually, RisingFury, since talking with you is what made me find this piece of fascinating info

Another explanation for the Bethlehem star is that it might be Jupiter and Saturn very close together - within less then a degree. That happens every 20 or so years. One such occurance is in October of "year -6" and another in December of year 14. Might also be Venus and Jupiter, but not sure if they'd appear in the "correct" part of the sky.

Here you pinpoint the problem yourself, by saying 'might'. It doesn't matter how good our present-day technology is if we don't know what to look for. We don't have a clear enough account of exactly what the Bethlehem star was, no one at that time gave any, and therefore we don't know exactly what to point our super-technology at. I've even read suggestions that it might have been a comet.

That's why we need clear references that can translate the divide of time, so to speak
Like we do on the Northern star.

There are many references of dragons in various civilisations that never had any contact. Does that mean that dragons were real, even though we can't find them today?

I have no idea what you are talking about. Or what comparison you are trying to make. Sorry about that.

Stars don't just go poof and vanish into pitch black. There's always stuff left behind, at least in a timeframe as short as we're talking about...

Material glows after the star dies because it's ionized, so you can clearly see it with a telescope...

That's why I used the term _un-natural_ about the star-behavior I was looking for

 

[Warped]

In a Milky Way sized galaxy, a star goes supernova once every roughly 50 years. Only a few of those will be visible with the naked eye from Earth.

Stars live for a minimum of a few millions to a maximum of a few billion years before they die, so I hope you're not actually watching to see one evolve in front of your eyes.

Some red dwarfs can burn for trillions of years.

 

[DaveS]

Some red dwarfs can burn for trillions of years.

Uh, no they can't. That would be against the laws of physics! The estimated age of the universe itself is about 14.6 billion years and given than billion is less than trillion, you're reply is very much off the mark, no where near close to be considered correct.

 

[dgatsoulis]

Uh, no they can't. That would be against the laws of physics! The estimated age of the universe itself is about 14.6 billion years and given than billion is less than trillion, you're reply is very much off the mark, no where near close to be considered correct.

I think that Warped meant that [ame="http://en.wikipedia.org/wiki/Red_dwarf"]red dwarfs[/ame] can have a lifespan much greater than that of the sun, not that a red dwarf has been burning for that long already. (which is impossible)

The lower the mass of a red dwarf, the longer the lifespan. It is believed that the lifespan of these stars exceeds the expected 10 billion year lifespan of the sun by the third or fourth power of the ratio of their masses to the solar mass; thus a red dwarf with 0.1 solar mass may continue burning for 10 trillion years.

 

[RisingFury]

Are you suggesting that if a star collide with a black-hole that a supernova would then always be the result of such collision?
That does not appear to be what current mainstream theories believe according to the wiki-page: Supernova - Wikipedia, the free encyclopedia

SN 1054 is called a core-collapse supernova, on the wiki-page, and there are no suggestions of any collisions being the cause for the core-collapse.
So apparently this star followed the current established mainstream rules for star-behavior, so to speak, and thus didn't do anything un-natural.

I said collapse, not collide.





The Zodiac starsign apparently dates back to around year -1000 (1000 BC), so that's at-least 3000 years we can go back without ending up in complete randomness.
The shorter we go back, the more precise we can be of-course, so even here I don't disagree with you






Any star they could see, that is still visible, we can see to. I agree with you on that.

But for exactly the reason you point out, earlier limitations in observing capabilities relative to present-days, we are limited to using only the stars we can be relatively sure are identified the same by them and us. We can't use our own recent discoveries in a historic context, since they are exactly that; recent discoveries. But Polaris is a long-known star, 2000 years of history, and well-known, and thus is the type of star we can be pretty sure is identified the same by both them and us (It was easy enough to observe distinctively even back then)

Incidentally, I just read this about Polaris:

Link: Polaris - Wikipedia, the free encyclopedia
Not exactly what I was looking for, since it's not missing, but since it may be an anomaly it's in the same ball-park. Another possible opportunity to learn something further, maybe
I've got to thank you for that actually, RisingFury, since talking with you is what made me find this piece of fascinating info

Well, let's say for example Polaris was well referenced in ancient texts as being the pole star, with accuratelly measured error to the actual pole and that it's gone today. The first thing you do is account for stellar drift and in this case precession as well. If there are still no visible stars around that would fit the description, you survey the area with a telescope, to see if there are remenants left over.

Here you pinpoint the problem yourself, by saying 'might'. It doesn't matter how good our present-day technology is if we don't know what to look for. We don't have a clear enough account of exactly what the Bethlehem star was, no one at that time gave any, and therefore we don't know exactly what to point our super-technology at. I've even read suggestions that it might have been a comet.

Yea, but what else should we do in this case? We're looking for possible events. A bright object that appears in the sky for a while and then disappears? What options do we have? A combination of two planets close together, a comet, a sudden brightening of a star, possibly a failed nova, or a nova itself. For one, we can't really be sure that it happened, we can't really be sure that the description is correct (given the source text has been translated and modified so many times over time) and even if it was true, there might be a more reasonable explanation, then our stellar models not being correct...



As for the dragon analogy...

What I meant is that you're looking through historical sources to try to find events, but just because they're referenced, that doesn't mean that they occured... just like dragon that don't exist


As for your question about stars not fitting stellar models... I very much doubt you'll find any annomalies by looking through historical texts... the reason is that even if you find something weird that turns out to be correct, you don't have enough data to actually figure out what might have been different about the star. You might know that before it disappeared it glowed red and twinkled a lot and then disappeared suddenly without brightening... but given that that's as much as you can get, the description is still subject to interpretation.

A much better chance of finding something wrong with our stellar models would be to actually survey the sky - you have hundreds of billions of star in just this galaxy, at various stages of their development. If you're gonna find an annomally, you're gonna find it there. There *are* people activelly looking for annomalies with the goal of toppling currently established laws of Physics, but their research is on the cutting edge. That's how you get rich and famous in science...

Some red dwarfs can burn for trillions of years.

Err...nooo, most likelly not.
As far as we currently understand the stars, they typically hold enough fuel to burn from a billion to ten billion stars. The more massive a star is, the faster it will burn. Some very massive stars - 150 solar masses - burn for only a few million years before going supernova. While it's true that red dwarfs can burn a long time, it's still not trillions of years... the highest predictions I've heard range in the few ten billion. We know of a few stars that are almost as old as the universe itself.

 

[T.Neo]

From Wikipedia- Red Dwarf: Description and characteristics:

The lower the mass of a red dwarf, the longer the lifespan. It is believed that the lifespan of these stars exceeds the expected 10 billion year lifespan of the sun by the third or fourth power of the ratio of their masses to the solar mass; thus a red dwarf with 0.1 solar mass may continue burning for 10 trillion years.

Not sure if that's old or incorrect data though.

 

[RisingFury]

From Wikipedia- Red Dwarf: Description and characteristics:

Not sure if that's old or incorrect data though.

I asked my professor about that and he said he was sceptical. He said optimistically he'd put them at 100 billion years.

 

[Hielor]

IThere *are* people activelly looking for annomalies with the goal of toppling currently established laws of Physics, but their research is on the cutting edge. That's how you get rich and famous in science...

Alternately (and more likely), that's how you can manage to lead a scientific career without anyone ever knowing your name.

I asked my professor about that and he said he was sceptical. He said optimistically he'd put them at 100 billion years.

Hey, it's on Wikipedia, so you know it must be right!

One of the sources quoted for the trillion-year number is http://spiff.rit.edu/classes/phys230/lectures/planneb/planneb.html ...which looks rather less than academic, but looks to be from a professor of some kind

 

[T.Neo]

This is cited on the Proxima Centauri page, it seems more academic to me.

 

[JEL]

Yea, but what else should we do in this case? We're looking for possible events. A bright object that appears in the sky for a while and then disappears? What options do we have? A combination of two planets close together, a comet, a sudden brightening of a star, possibly a failed nova, or a nova itself. For one, we can't really be sure that it happened, we can't really be sure that the description is correct (given the source text has been translated and modified so many times over time) and even if it was true, there might be a more reasonable explanation, then our stellar models not being correct...

That was exactly my point
The longer we try to go back in history, the more distinctive the description has to be to make sure we are not mistaking it for something else. That's why I suggested using star-signs for long-term history (although you make an excellent point further below about why that's not really useful for the purpose discussed in this thread )

As for the dragon analogy...

What I meant is that you're looking through historical sources to try to find events, but just because they're referenced, that doesn't mean that they occured... just like dragon that don't exist

Ok I see what you mean now Questioning the believability of history. I believe that's more of a philosophical debate though. For the subject of this thread I am just going on the assumption that people before us are telling the truth, but ofcourse we can never be absolutely sure if they are if we weren't there ourselves.

I very much doubt you'll find any annomalies by looking through historical texts... the reason is that even if you find something weird that turns out to be correct, you don't have enough data to actually figure out what might have been different about the star. You might know that before it disappeared it glowed red and twinkled a lot and then disappeared suddenly without brightening... but given that that's as much as you can get, the description is still subject to interpretation.

Yes, that pretty much defeats using historic accounts for the purpose discussed in this thread I suppose.

A much better chance of finding something wrong with our stellar models would be to actually survey the sky - you have hundreds of billions of star in just this galaxy, at various stages of their development. If you're gonna find an annomally, you're gonna find it there.

That leaves us with this; zero stars are known missing for un-natural reasons since Hubble was launched in 1990.
Before 1990 we aren't sure to the same degree of certainty.
Well, that's good enough for now

 

[Nerull]

Uh, no they can't. That would be against the laws of physics! The estimated age of the universe itself is about 14.6 billion years and given than billion is less than trillion, you're reply is very much off the mark, no where near close to be considered correct.

White dwarfs take longer to cool into black dwarfs than the universe has existed, but this does not mean it is impossible, just that it hasn't happened yet.

---------- Post added at 07:12 PM ---------- Previous post was at 07:06 PM ----------

However, if the North star could not be seen today we would be pretty certain it was once there simply because many references of it are very clear and hard to mistake for other stars.

Polaris has not been the north star for all of recorded history. For reference, the Great Pyramids were built in ~2560BC

 

[JEL]

Polaris has not been the north star for all of recorded history.

Sorry if I seemed to indicate that by using the term north star. I just did that because it's such a common name for it in our present day, and since polaris means basically the same thing (stella polaris / polar star)
I'm not sure what would be the most accurate name for it if I should use one that does NOT imply it to pinpoint the pole at ALL times. On the wiki-page it seems to have quite a lot of different names.

Anyway, to quote myself:

All the known star-signs are still there (that covers at-least a few thousand years of human history), all the stars used for navigation throughout relatively modern times are still there (that's at-least 500 years of human history)

Polaris has been used for navigation for atleast 500 years, and is a known star atleast since the [ame="http://en.wikipedia.org/wiki/Almagest"]Almagest[/ame] was compiled around year 150