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Star populations by spectral classes and masses

  1. Jan 23, 2010 #1
    I need the % of stars in our galaxy, sorted by spectral classes and also by masses. Is there any such information somewhere ?
  2. jcsd
  3. Jan 23, 2010 #2
    Of course! There is a wealth of information on this. Wikipedia will spell out for you both the masses and populations of the spectral classes.
  4. Jan 23, 2010 #3
    I already searched (especially Wikipedia) and didn't found the % I was looking for. The only document (a picture in some PowerPoint document !) gave the percentage of stars of given masses :

    41% for M < 0.25 M_Sol
    28% for 0.25 M_Sol < M < 0.5 M_Sol
    19% for 0.5 M_Sol < M < 1 M_Sol
    8% for 1 M_Sol < M < 2 M_Sol
    3% for 2 M_Sol < M < 4 M_Sol
    ~1% for M > 4 M_Sol

    The trouble is that the document isn't clear and precise enough about the source of this data (where does it come from ?)
    I also need something similar about the spectral classes.

    I simply need more, so this is why I'm asking for some help on this subject.
  5. Jan 23, 2010 #4
    Wikipedia cites their data for masses and populations in the table in section 2 of the Spectral Classification article. If you need a more reliable source, any good astronomy textbook should have the information you need in an appendix.
  6. Jan 23, 2010 #5
    Well, on the wikipedia article :


    we can find spectral class populations in % but only for the main sequence stars. I need something more general. Also, the Wikipedia article doesn't say anything about populations sorted by masses.
  7. Jan 24, 2010 #6


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    Check Vizier, they have spectral survey databases.
  8. Jan 24, 2010 #7

    Vanadium 50

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    I think you will have a hard time, as this is poorly known. Most stars are small and dim red dwarfs, and we can't see them well. The best measurements are probably from 2MASS, which was an all-sky survey in the IR. I don't know if anyone has attempted to take the 2MASS data and convert it into the format you're looking for.

    Fundamentally the problem is bias - it's easy to see big, bright, blue stars, so counting what you see in the sky gives you a sample that is biased, big, bright and blue.
  9. Jan 24, 2010 #8
    Q : How can we know if a randomly picked star is in the main sequence ?

    More precisely, suppose I have the following innformations : Radius, Luminosity, Absolute Magnitude, Spectral class and surface temperature. Is there a simple mathematical procedure to say if it's a main sequence star ?
    Last edited: Jan 24, 2010
  10. Jan 24, 2010 #9
    depending on the limits of main sequence cant that be taken from a HR diagram? L vs Teff will put you somewhere on the plane...
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