Stars A and B form a binary system

PHYSICS · Single correct · A Level · Physics · Astrophysics · Astrophysics

Problem

Stars A and B form a binary system. Star A has a radius of

8.0\times10^{8}\,\text{m}

and a surface temperature of

7.0\times10^{3}\,\text{K}

. Star B has a surface temperature of

5.0\times10^{3}\,\text{K}

and an unknown radius

R_B

. The combined luminosity of the two stars is

1.4\times10^{27}\,\text{W}

. If both stars behave as blackbodies, which value is closest to

R_B

? (a)

1.3\times10^{9}\,\text{m}

(b)

8.2\times10^{8}\,\text{m}

(c)

4.7\times10^{8}\,\text{m}

(d)

1.8\times10^{9}\,\text{m}