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Estimating the Mass of the Companion Star

binary star animation
Credit: NASA

The star in question can be determined by its spectral classification to be a type OB supergiant. Using various measurements of distance, luminosity, and interstellar reddening, its mass can be reasonably determined. The absolute lower limit, which is what we are interested in for determining the lowest possible mass of the visible companion is about 9 solar masses. Further research has established that it is more likely around 30 solar masses.

Return Click here to return to solve for the mass of Cyg X-1.

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