Two identical spherical exoplanets orbit identical stars at the same orbital radius
PHYSICS · Single correct · IB Diploma Programme · Physics · The greenhouse effect · The greenhouse effect
Problem
Two identical spherical exoplanets orbit identical stars at the same orbital radius. Planet A has an albedo of 0.30 and an infrared emissivity of 1.0. Planet B has an albedo of 0.60 with the same emissivity. Neglect all heat sources other than starlight. Which statement correctly compares their equilibrium surface temperatures?
(a) Planet B is warmer than Planet A because its higher albedo traps more radiation.
(b) Planet A is cooler than Planet B because it emits more radiation per unit area.
(c) Planet B is cooler than Planet A because it absorbs less stellar energy.
(d) Both planets reach the same equilibrium temperature because their emissivities are identical.