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Do Stars Actually Still Exist?
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If it is true that light from stars has taken millions of years to reach us, than how do we know that these stars are still in existence? Which raises a further question that the Universe may now no longer exist either, and we are now just seeing an image of what was once out there in space.
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>>>how do we know that these stars are still in existence?
We don't.
However the frequency of light coming from a particular star will provide an indication of how far through its life that star was when the light left it, so it's possible to make a reasonable guess as to whether that star still exists. (Its clear than millions don't).
>>>the Universe may now no longer exist either
Well you and I form part of the Universe. Are you suggesting that we don't exist?
"Cogito ergo sum" - René Descartes ;-)
We don't.
However the frequency of light coming from a particular star will provide an indication of how far through its life that star was when the light left it, so it's possible to make a reasonable guess as to whether that star still exists. (Its clear than millions don't).
>>>the Universe may now no longer exist either
Well you and I form part of the Universe. Are you suggesting that we don't exist?
"Cogito ergo sum" - René Descartes ;-)
Most stars are assured of lifespans measured in the billions of years. Our own Sun for example has an estimated 10 billion year life span, and we are thought to be around half way through that period. One of my favourite large numbers is the estimated 600 million tons of hydrogen burned per second, with a lifespan of 10 billion years! My brain cannot process that number :)
The overwhelming majority of stars you can see with the naked eye in the sky are actually 10s ,maybe hundreds of light years away.
Given that age of the light arriving to us now,(10s - 1000s of light years) and the likely life span of the stars (billions of years) it is very likely that the more easily observed stars in the sky are still there, merrily burning away.
It is true to infer that many stars will have died out, those estimated to be millions of light years away from us and whose light is only just reaching us now - but you would need something like the Hubble Telescope to see their light. It is also important to remember that star formation and death is a process, and that whilst stars are going out, new ones are being born.
So, the idea that stars whose light is only just reaching us have already burned out is a reasonable supposition. What I do not quite understand is how you get to the universe ceasing to exist from that supposition......
The overwhelming majority of stars you can see with the naked eye in the sky are actually 10s ,maybe hundreds of light years away.
Given that age of the light arriving to us now,(10s - 1000s of light years) and the likely life span of the stars (billions of years) it is very likely that the more easily observed stars in the sky are still there, merrily burning away.
It is true to infer that many stars will have died out, those estimated to be millions of light years away from us and whose light is only just reaching us now - but you would need something like the Hubble Telescope to see their light. It is also important to remember that star formation and death is a process, and that whilst stars are going out, new ones are being born.
So, the idea that stars whose light is only just reaching us have already burned out is a reasonable supposition. What I do not quite understand is how you get to the universe ceasing to exist from that supposition......
Despite the linear expansion of space, Hubble pictures of galaxies some 12 billion light-years away from us, show galactic density to be pretty much the same as it is in our neighbourhood. This suggests that new material (hydrogen) is regularly and continuously coming into being to fill the void created by the expansion, at the rate of one hydrogen atom in a space of about 500,000 cubic metres during the course of a year, from which new stars and galaxies are regularly and continuously coming into being.
Most stars (the huge blobs of hydrogen) use up their hydrogen by nuclear conversion at their cores and eventually stop radiating heat and light. Stars which are more than about three solar masses use up their hydrogen rapidly and blow up in a supernova explosion which produces elements heavier than iron.
There is, therefore, no “end” of the universe, it simply stretches forever in every direction, with old stars dying and new stars born from the massive clouds of hydrogen.
Most stars (the huge blobs of hydrogen) use up their hydrogen by nuclear conversion at their cores and eventually stop radiating heat and light. Stars which are more than about three solar masses use up their hydrogen rapidly and blow up in a supernova explosion which produces elements heavier than iron.
There is, therefore, no “end” of the universe, it simply stretches forever in every direction, with old stars dying and new stars born from the massive clouds of hydrogen.
Icenian, does your first paragraph suggest you believe in the Steady State theory?
Nearby galaxies, like Andromeda, are similar to our own. If you observe a blue supergiant star in Andromeda (2 million light years distant) then it will not exist now because such stars have lifespans of only a few hundred million years.
A red dwarf star, observed in the Andromeda galaxy, is still likely to be there as they have very long lifetimes.
Distant galaxies, say 13 billion light years away, are quite different to our own.
Nearby galaxies, like Andromeda, are similar to our own. If you observe a blue supergiant star in Andromeda (2 million light years distant) then it will not exist now because such stars have lifespans of only a few hundred million years.
A red dwarf star, observed in the Andromeda galaxy, is still likely to be there as they have very long lifetimes.
Distant galaxies, say 13 billion light years away, are quite different to our own.
Interesting answers. What I find puzzling is that if there are trillions of stars out there, then new constellations of stars should be appearing to us all the time as their 'light reaches us'. However this is clearly not the case.
Is it possible that the 'universe' is now just a blank void and nothing exists beyond our own sun?
Is it possible that the 'universe' is now just a blank void and nothing exists beyond our own sun?
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