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Name: j p reed
Status: N/A
Age: N/A
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Date: 1993 - 1999

I am doing a project on astronomy and positions of thethe stars/constellatio My question is how accurate are the formulas that we use to figure out the positions of the stars when they are applied to 2 or 3 millenia into the future. Are those positions that we say they will be in 2500 or even 3500 (if we're still around) as accurate as those that we predict for next year?

What you're asking about is the "proper motion" of stars. Only the c closest stars have any appreciable proper motion; the largest known is for Barnard's Star with a proper motion of:

"an exceptional 10 arcseconds per year"

(60 arcseconds = 1 arcminute, 60 arcminutes = 1 degree, both the Sun and the Moon subtend about one half a degree in the sky as seen from the surface of the Earth [which is why we have such spectacular total solar eclipses!])

So, Barnard's Star will move about 3 degrees in a thousand years. Most stars have a proper motion much less, and their change in position in the night sky over one or two thousand years will not be noticeable to the naked eye.

To actually answer your question (finally!), the formulas used to predict a stars position are *very* accurate over time scales of a few thousand years.


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