The apparent magnitude of a star is observed to vary between m = +0.4 and m = +0.1 because the star pulsates and hence continuously changes its radius and temperature. When at its peak brightness, the star’s radius has increased by a factor of two compared to its value at the mini- mum brightness. Determine the value of T+/T−, where T+ is the temperature when the star is at its peak brightness and T− is the temperature when the star is at it minimum brightness. Note: we expect T+/T− < 1 because the star’s temperature decreases as its radius increases.

The apparent magnitude of a star is observed to vary between m = +0.4 and m = +0.1 because the star pulsates and hence continuously changes its radius and temperature. When at its peak brightness, the star’s radius has increased by a factor of two compared to its value at the mini- mum brightness. Determine the value of T+/T−, where T+ is the temperature when the star is at its peak brightness and T− is the temperature when the star is at it minimum brightness. Note: we expect T+/T− < 1 because the star’s temperature decreases as its radius increases.