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Most distance methods are luminosity-based: you measure an object's flux, assume it has a particular luminosity, and then determine the distance from that using the inverse-square law. So the question becomes: how do you determine the luminosity? The eclipsing-binary method uses the idea that a star's luminosity can be defined as $L = 4 \pi f_{s} R^{2}$, ...


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The key here is mass. In nonbinary systems (or other external factors) it can be a bit tough to determine mass of a star. You just see a point source of light; we can get spectral features which can in some instances be used to give us some idea, but it’s rather tough to otherwise get mass. If you do have mass (which you can get because binary stars are ...


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