Physics

Problem

Star A has apparent brightness

8.0 \times 10^{-13} \text{ W m}^{-2}

and its distance is 120 ly. Star B has apparent brightness

2.0 \times 10^{-15} \text{ W m}^{-2}

and its distance is 150 ly. The two stars have the same size. Calculate the ratio of the temperature of star A to that of star B.