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Pole Star - Help!

  1. Sep 4, 2006 #1
    I hope some of you will be able to help me.

    First, let me make sure I have this right. From what I understand, the five Pole Stars are:

    Polaris
    Al Deramin
    Deneb
    Vega
    Thuban

    My question is, what was the Pole Star between 9,000 BC and 10,000 BC? The length of time for each Pole Star doesn't seem to be uniformly set.

    Thank you!
    Myra
     
  2. jcsd
  3. Sep 4, 2006 #2

    DaveC426913

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    What an odd question.

    I've only ever known of two pole stars: Polaris and Vega. Vega was a pole star about 13,000 years ago. Between then and now, the axis pointed ... somewhere between those two.


    Update: OK, I've looked at the five stars you mention. They form a circle. Huh. You learn something new every day. I've learned of 3 new polestars!

    This page talks about what the pole was in the past. You should be able to extrapolate to the time you're looking for.

    [EDIT: Unless I beat you to it...]
     
    Last edited: Sep 4, 2006
  4. Sep 4, 2006 #3

    DaveC426913

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    Now you've gone and made me late for bed!

    It appears that these two stars are your best bets:
     

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  5. Sep 4, 2006 #4
    Dave, thank you! This has been a great help so far. I was stuck on Vega, because I can find references to it being the Pole Star between 13,000 BC and 11,000 BC. However, I can find NO mention of a Pole Star between then and around 3100 BC, when Thuban took over. The fact that there's no mention of a Pole Star for approximately 8,000 years is somewhat disconcerting to me, and with the research project I'm currently working on, even more so!

    Thanks for the charts as well, I'm going to be looking them over and doing some cross-referencing. This "lost pole star" has now become a challenge for me. :devil:
     
  6. Sep 7, 2006 #5

    Chronos

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    Humans were not very good at keeping records about anything they observed more than 5000 years ago.
     
  7. Sep 7, 2006 #6

    selfAdjoint

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    Why should there always be a pole star? Therer isn't one at the South celestial pole currently and I haven't heard the Aussies or Kiwis complain. They put the close-but-no-cigar Southern Cross on their flags.
     
  8. Sep 7, 2006 #7
    well, the southern cross points to the south celestial pole!
     
  9. Sep 7, 2006 #8

    selfAdjoint

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    Not good enough; that's just to say you can find two stars that line up on a north - south arc. You need another line to cross that to fix the location of the pole.
     
  10. Sep 7, 2006 #9

    I'm not sure, actually. Perhaps it's because it seems to be one of things that just "should always be." Like Santa Claus, you know?
     
  11. Sep 7, 2006 #10

    DaveC426913

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    I think the idea behind 'should always be' is this:

    A pole star is de facto the closest major star to the axis. There are ages where it's a good indicator and there are ages where it's a lousy indicator (accuracy-wise) but, frankly, there will always be a star that some early man would point to and say 'the stars rotate around about that point'.

    As per the page I found above that helped me set the path:

    Kochab is labelled in my diagram. And indeed, it is a lousy pole star. But it still works as a pole star.
     
  12. Sep 8, 2006 #11

    selfAdjoint

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    I think this is reading back. We don't know how the Greeks, let alone the Babylonians, really thought of things. Clearly if the naked eye can see down to magnitude X there's more dark space for the wandering apparent pole to traverse than there are magnitude X stars. And if Kochab is a "poor" pole star then it has a visible circle itself i.e. it isn't a pole star even to naked eye observation.
     
  13. Sep 8, 2006 #12
    Such as the Dogon tribe? Because, and for reasons utterly unknown, they knew that Sirius had a companion star which was not only completely invisible to the naked eye, but never officially discovered until 1926.

    I still have not found an explanation as to how they were able to do this.
     
  14. Sep 8, 2006 #13

    DaveC426913

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    Well, Polaris has a circle too - that doesn't stop it from serving as a pole star. Polaris' circle is only 0.5 degrees radius, but where do you draw the line? If Kochab were, say, 10x as far from the axis, it would still be good enough to guide wayfarers home.
     
  15. Sep 9, 2006 #14

    selfAdjoint

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    Ahh, you'd have to show me evidence that any of these mariners (early Greeks and Middle Easterners) ever navigated at night or our of sight of land.
     
  16. Sep 9, 2006 #15

    DaveC426913

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    Or what? Or they won't have ever had a reason to care where North is? Why is that limited to mariners?
     
  17. Sep 10, 2006 #16
    One interesting thing I noticed when looking at the 'track' of the NCP - is that almost in the middle of the era that Myra first asked about - around 9500 BC - the NCP would have been pretty damn close to globular cluster M92.
     
  18. Sep 10, 2006 #17

    DaveC426913

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    Hey, are you Carlos from ADP? Welcome!
     
  19. Sep 10, 2006 #18
    Yep! - 'tis me - Hi Dave!
     
  20. Sep 11, 2006 #19

    Chronos

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    Hmm, either the Vikings were lucky, or knew how to navigate by the stars. Actually, I have a conspiracy theory about this kind of 'ancient knowledge': Back in the day, there were plenty of very bright people who had already figured out the science behind things like 'dead reckoning' navigation. They also figured out it would be suicidal to keep written records of such 'witchcraft'.
     
    Last edited: Sep 11, 2006
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