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Can variable stars become quickly non variable and viceversa?

  1. Nov 11, 2011 #1
    Can a variable star become a non variable one? Or viceversa, can a non variable, as it is (almost) the sun, become quickly (say few thousands of years) a variable one? Is there any record (e.g. in the geological records) which shows that the sun had once a very different luminosity? Has this possibility ever been considered by astronomers?
     
  2. jcsd
  3. Nov 12, 2011 #2

    Astronuc

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    Staff: Mentor

    Perhaps the answer is - "it depends . . . "

    http://www.aavso.org/variables-what-are-they-and-why-observe-them?page=10

    See also - http://www.aavso.org/types-variables
    and - http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_types.html
    - http://ned.ipac.caltech.edu/level5/ESSAYS/Evans/evans.html


    http://www.aavso.org/stellar-evolution


    Stellar Physics: 2: Stellar Evolution and Stability, Volume 2 By Gennadii S. Bisnovatyi-Kogan


    One might also wish to purchase this book - Understanding Variable Stars (Cambridge Astrophysics)
    https://www.amazon.com/Understanding-Variable-Stars-Cambridge-Astrophysics/dp/0521232538/


    Then the question is - under what conditions would a variable star lose its variablity.
     
    Last edited by a moderator: May 5, 2017
  4. Nov 12, 2011 #3
    Yes, but I don't think this answers the question. Can we say for sure that, for instance, 10.000 years ago the sun had the same luminosity of today? I tend to say that it wasn't. If we look at the HR diagram we don't see thin evoultionary paths but thick lines, like a statistical fluctuation, as if stars could variate in luminosity and color at a specific fixed evolutionary state. Of course this is because the statistics is made of different stars, but we can't say for sure that this is the only cause. And we have not sufficient time record to exclude this eventaulity, for our as for other stars, since our meausrements are at best only 3-4 centuries old.
     
  5. Nov 12, 2011 #4

    Astronuc

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    Staff: Mentor

    Perhaps this will help

    Observed Variability of the Solar Luminosity
    Annual Review of Astronomy and Astrophysics
    Vol. 26: 473-507 (Volume publication date September 1988)
    http://www.annualreviews.org/doi/abs/10.1146/annurev.aa.26.090188.002353

    http://en.wikipedia.org/wiki/Solar_variation (No endorsement expessed or implied)

    The Sun-Like Activity of the Solar Twin 18 Scorpii
    http://arxiv.org/ftp/astro-ph/papers/0703/0703450.pdf
    One can look at the loss of solar mass of 100 years, 1000 years, 10 ky, and calculate the impact of nominal luminosity.
     
  6. Nov 12, 2011 #5
    Thanks for the effort, it directed me to: http://cc.oulu.fi/~usoskin/personal/aa15843-10.pdf

    According to the above the sun's irradiance changed only about 2/1365 over the past 10.000 years. Hmmm... I'm skeptic... :uhh: ... Anyhow, thanks so far.
     
  7. Nov 12, 2011 #6

    Drakkith

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    Skeptic of what?
     
  8. Nov 13, 2011 #7
    Of the irradiance stability of the sun over periods between 5.000-1.000.000 years.
     
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