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The End of Stars?

  1. Aug 13, 2010 #1
    I'm collecting information to write a science fiction novel set very, very far into the future. Without going into the plot, it attempts to explore concepts of isolation, eternity, and the collapse of the universe itself (modeled on the Big Freeze cosmological theory). To this end, I am curious how long the universe has before new stars become something of a rarity (as in, say, less than one star birth per million years per galaxy).
     
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  3. Aug 14, 2010 #2

    Chronos

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    At least twice its current age [about 13.7 billion years], and very likely more. There is a finite amount of uncollected gas and dust in the universe, but, appears to be more than enough to sustain stellar formation for many billions of years. A much older universe would, however, be dominated by white dwarfs, neutron stars, and low mass stars. Massive new stars will become increasingly rare over the next 10 billion years, IMO.
     
  4. Aug 20, 2010 #3
    Of course such estimates are based on the amount of matter we detect in the visible universe. However, scientists are constantly telling us that this visible part is only a very small fraction of the undetectable part. If that is true, then our calculations can be severely skewed.

    =====================================================

    Excerpt

    So how big is the universe? No one knows if the universe is infinitely large, or even if ours is the only universe that exists. And other parts of the universe, very far away, might be quite different from the universe closer to home. Future NASA missions will continue to search for clues to the ultimate size and scale of our cosmic home.
    http://www.nasa.gov/audience/foreducators/5-8/features/F_How_Big_is_Our_Universe.html
     
  5. Aug 28, 2010 #4
    Hi Angry Citizen

    A very useful series of papers relevant to your quest was produced by Fred Adams, Greg Laughlin and Peter Bodenheimer. Adams & Laughlin also collaborated on a popularisation of their work, "The Five Ages of the Universe", which is essential background material for any extreme Future setting.

    The papers are available online and I'll provide links to them here...

    http://arxiv.org/abs/astro-ph/9701131" [Broken]

    http://iopscience.iop.org/0004-637X/482/1/420/pdf/0004-637X_482_1_420.pdf"

    http://www.astroscu.unam.mx/rmaa/RMxAC..22/PDF/RMxAC..22_adams.pdf" [Broken]

    ...in summary the Galaxy will shine and make stars at a fair pace for about 10 trillion years. Regular star formation will sputter to a halt by about then and the only new stars will come from degenerate object collisions (i.e. brown dwarfs, white dwarfs and neutron stars) roughly once every 100 billion years. As the low mass stars produced by brown dwarf collisions will last ~10 trillion years, that means about ~100 will shine, very weakly, at any one time. Once every ~trillion years two white dwarfs will collide and make a supernova. Otherwise the Galaxy will only glow with the wan infra-red light of white-dwarfs being heated by dark-matter annihilation.
     
    Last edited by a moderator: May 4, 2017
  6. Sep 3, 2010 #5
    They curiously aren't. Unless there is something that we've *really* gotten wrong, then the amount of dark matter isn't going to affect the evolution of the universe over the next tens of billions of years.

    However, there are some good ways of getting amount of hydrogen and helium in the universe. We don't know what dark matter is, but we know that it's stuff that can't form stars.

    Yes but it turns out that what we do know isn't going to change much how long it will be before the stars burn out.
     
  7. Sep 3, 2010 #6
    If you are thinking of science fiction scenarios take a look at

    http://en.wikipedia.org/wiki/Dyson's_eternal_intelligence

    Note that Dyson wrote his paper when we didn't know that the universe was accelerating. It turns out that his scenario probably won't work in that sort of situation.
     
  8. Sep 3, 2010 #7
    He also didn't factor in proton-decay, phase transitions and a whole bunch of other Cosmic Eschatological possibilities. Eternity isn't just a really long time... it's forever!
     
  9. Sep 3, 2010 #8

    600px-CMB_Timeline75.jpg
    Prevailing Universe model of the origin and expansion of spacetime and all that it contains

    [tex]H_0 = 2.3298 \cdot 10^{- 18} \; \text{s}^{- 1}[/tex] - Hubble parameter (WMAP)
    [tex]\Omega_b = 0.0456[/tex] - Lambda-CDM baryon density
    [tex]\Omega_h = 0.0033[/tex] - Lambda-CDM heavy baryonic matter and neutrino density

    Universe heavy baryonic matter stellar burn rate integration by substitution:
    [tex]R_b = \frac{d \Omega}{dt} = \Omega_h H_0 = 7.688 \cdot 10^{-21} \; \frac{d \Omega}{\text{s}}[/tex]

    Universe heavy baryonic matter stellar burn rate:
    [tex]\boxed{R_b = 7.688 \cdot 10^{-21} \; \frac{d \Omega}{\text{s}}}[/tex]

    Universe baryonic matter stellar epoch burn lifetime integration by substitution:
    [tex]T_s = d \Omega \cdot dt = \frac{\Omega_b}{R_b} = \frac{\Omega_b}{\Omega_h H_0} = 5.931 \cdot 10^{18} \; \text{s} = 1.879 \cdot 10^{11} \; \text{y}[/tex]

    Universe baryonic matter stellar epoch burn lifetime:
    [tex]\boxed{T_s = \frac{\Omega_b}{\Omega_h H_0}}[/tex]

    Universe baryonic matter stellar epoch burn lifetime:
    [tex]\boxed{T_s = 1.879 \cdot 10^{11} \; \text{y}}[/tex]

    Universe age:
    [tex]T_u = \frac{1}{H_0} = 4.292 \cdot 10^{17} \; \text{s} = 1.36 \cdot 10^{10} \; \text{y}[/tex]

    [tex]\boxed{T_u = 1.36 \cdot 10^{10} \; \text{y}}[/tex]

    Number of present Universe ages required to complete baryonic matter stellar epoch burn lifetime:
    [tex]n_a = \frac{T_s}{T_u} = \frac{\Omega_b}{\Omega_h} = 13.818[/tex]

    The Universe will be producing stars for a very long time...

    Reference:
    http://en.wikipedia.org/wiki/Lambda-CDM_model#Parameters"
    http://en.wikipedia.org/wiki/Heat_death_of_the_universe" [Broken]
    http://en.wikipedia.org/wiki/Universe" [Broken]
     
    Last edited by a moderator: May 4, 2017
  10. Sep 3, 2010 #9
    It depends on your point of view. This might be an odd thing to say but, I don't think that 13 times the current lifetime of the universe is an long time. There are a billion people in China, and if you handed everyone in China and India a century, you'll run out of years.

    Also what's interesting is that the projected lifespan of a red dwarf is 5 trillion years, which means that a red dwarf will live most of its life in an era in which no new stars are being produced.
     
  11. Sep 3, 2010 #10
    If the production rate is proportional to the gas remaining then that 'lifetime' number is really an e-fold time. So we can compute how long it'll take for the present star-forming rate of ~10/year will take to decline to 1/million years. Thusly ~ ln(1E+7) = 16.11, so multiply that by the 187.9 billion years Orion1 derived and we get ~3.028 trillion years before the star formation rate slows to just 1 per million years. In another ~2.2 trillion years after that it declines to the collisional production rate of ~1/0.1 trillion years, thus marking the effective end of normal star-formation processes.

    Another collisional outcome which I've read about is the collision of a brown dwarf and a white dwarf, which should create a relatively bright star able to burn for several billion years. Such a star would burn out long before others like it would form, thus it would have a very, very lonely sky in visible light. Imagine the impact of the discovery of the Galaxy glowing wanly in IR.
     
    Last edited: Sep 3, 2010
  12. Sep 3, 2010 #11

    250px-RedDwarfNASA.jpg
    An artist's conception of a red dwarf star. Red dwarfs constitute the majority of all stars

    According to my understanding, there was an epoch in the Universe during the first generation stars when there were absolutely no red dwarfs. It is probable that a heavy baryonic matter stellar core 'seed' is required to stellar dynamically generate a red dwarf star from a hydrogen and helium nebula. And interstellar nebular heavy baryonic matter can only be produced from a supernova explosion from at least a first generation star.

    220px-Red_dwarf_lifetime.png
    The predicted main sequence lifetime of a red dwarf star plotted against its mass relative to the Sun

    The red dwarf baryonic matter stellar burn rate increases exponentially as mass is increased linearly. Although red dwarfs have relatively low burn rates, they also have the highest stellar population density in the Universe, therefore red dwarfs make the largest contribution to the Universe heavy baryonic matter stellar burn rate, followed by the remaining main sequence stars population densities, and then followed by stellar giants and supernova explosions.

    The red dwarf stellar population density is also an indication that the Universe has already experienced a large number of supernova explosions due to the fact that red dwarf stars are inseparable from 'supernova residue', and the Universe will continue generating supernovae until the end of the stellar producing epoch.

    The Universe will eventually reach an epoch where white, red and brown dwarf stars completely occupy the total stellar population density, in an epoch in which no new stars are being produced by normal star-formation processes.

    Reference:
    http://en.wikipedia.org/wiki/Red_dwarf" [Broken]
     
    Last edited by a moderator: May 4, 2017
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