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When you have observed the complete revolution of a star around an other one, you can derive the mass of the double star system (the sum of the masses) by using the Kepler's third law. That's OK.

I have heard that you can find the mass ratio of the system by using spectroscopy. Then, with the sum and the ratio, you can derive each mass separately.

My question is : how can we determine the mass ratio with spectroscopy ?

Kind regards

Jeff

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# Mass of doubles stars

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