How to find orbital radius of star in a binary system using redshift and orbital period data? [duplicate]
Possible Duplicate: About binary stars and calculating velocity, period and radius of their orbit I am given the non-redshifted wavelength of the EM radiation from one of the stars, the ...
I know that for close by stars (<50 LY) we can use the parallax effect. And for distant galaxies we use red-shift (& hubble's constant). So how do we measure how far is a star lets say 50,000 ...