Spica (in Virgo) and Hador (in Centaurus) have about the same temperature. However, Hador has roughly 4 times the luminosity of Spica. What can one determine about the relative radii of these two stars? Spica is about

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Quizplus · Accepted Answer

The luminosity of a star is directly related to its surface area (and thus the square of its radius) and its surface temperature. Given that Spica and Hador have about the same temperature but Hador is four times as luminous, it means Hador has a larger surface area. Since luminosity scales with the square of the radius, to get a fourfold increase in luminosity, the radius (and thus diameter) of Hador must be twice that of Spica, making Spica half the diameter of Hador.

Spica (In Virgo) and Hador (In Centaurus) Have About the Same