Question

If the stars Betelgeuse and Rigel each have the same luminosity, but the temperature of Betelgeuse is lower than Rigel, which star has the greater surface area?

Answer 1

Betelgeuse

Step-by-step explanation:

Stars luminosity is given by the Stefan–Boltzmann law, since the emitted energy is treated as black body radiation:

`L=\sigma AT^4`

Here
`\sigma` is the Stefan–Boltzmann constant, A is the surface area and T is the temperature. According to this formula, if both stars have the same luminosity, then the lower temperature star must have a greater surface area.