Determine the radius of the star Alphard (a Hydra), if its temperature is 4000 K, and the luminosity is 430 times the luminosity

Determine the radius of the star Alphard (a Hydra), if its temperature is 4000 K, and the luminosity is 430 times the luminosity of the Sun (Lc = 4 * 10 ^ 26Bt).

decision
L = 4пR ^ 2 0T ^ 4; R ^ 2 = L / 4n0T ^ 4; R ^ 2 = 430 • 4 • 10 ^ 26/4 • 3.14 • 5.67 • 10 ^ -8 (4 • 10 ^ 3) ^ 4; R = 3 * 10 ^ 7 (km).

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