點樣知道同第2個星體距離幾遠同質量

[H]bunbunbunbun

Distance between earth and star can be measured by the difference between the angle observed at different times with reference to other background stars (assuming that the background stars are stationary)

Mass of a star can be measured by the doppler effect (i.e. red shift/blue shift)
this method measures the wavelength of light emitted by the star, which changes over time due to circular motion. (change in wavelength/actual wavelength = velocity/speed of light)
with the calculated velocity and the period, you can calculate the semimajor axis of orbit.
Then you can use Kepler's third law to fin the mass of the binary system (stars move in pairs, so you'll have to find the doppler shift of the other star/ assume one is neglectable in order to find the mass of a particular star.)