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Martin
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Im trying to see how they determine how many light a star

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I'm trying to see how they determine how many light a star is from earth. What method did they use?
Submitted: 2 years ago.
Category: General
Expert:  Martin replied 2 years ago.
Hello and welcome. There is not just one method. The more method used the best approximation we can get. Also some method just don't work when a star is too far. Hyperphysics (a science site i always found well done) have a good overview of the different method:

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/distance.html

You can also look at more methods here from UCLA:
http://www.astro.ucla.edu/~wright/distance.htm
Customer: replied 2 years ago.

Very interesting, at such great distance how accurate is it(+/- light years)? also would it matter if the rotation on the earth isn't perpendicular to the star if so how do they account for this. Thanks

Expert:  Martin replied 2 years ago.
Here is a bit of discussion about the accuracy in % of error or the distance:
http://www.uwgb.edu/dutchs/cosmosnotes/distance.htm
(look at the table in the middle of the page). As you can see the accuracy decrease the farthest is the star. For some method and condition the error can be as much as 25%.

SIM (Space Interferometry Mission) was a NASA project that wanted to increase accuracy but got it's funding canceled:
http://science.nasa.gov/missions/sim/
Martin, Engineer
Category: General
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Experience: i'm 41 and i never stopped studying and experimenting
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Martin
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i'm 41 and i never stopped studying and experimenting