Question

A red star and a white star radiate energy at the same rate which star is bigger?

• A. Red
• B. White
• C. Both have same size
• D. Can't say anything

Answer 1

The correct option is A Red

Red star must be bigger because the energy radiated by star is proportional to the square of its radius times fourth power of its temperature i.e.

$Energy\propto r^2{T}^4$

where, r is the radius and T is the temperature

A red star would be half the temperature of the white star so it would need to have radius 4 times the white star to emit the energy at the same rate.