Page 610 - 89 history of astronomy_opt

calculated that the mass of Sirius equals
two of our suns, and its intrinsic bright-
ness equals twenty suns; but the compan-
ion, having a mass equal to our sun, has
only a five-hundredth part of the sun’s bright-
ness.
Spectroscopic Binaries .–On measuring
the velocity of a star in the line of sight at
frequent intervals, periodic variations have
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