Cepheid variables pulsate because they contain a layer that alternately blocks photons while heating and then becomes transparent to photons as it expands. What substance composes this layer?

Question

Quizplus · Accepted Answer

Cepheid variables pulsate due to a layer of ionized helium. This layer alternately blocks and allows the passage of photons as it heats and expands, driving the pulsation.

Cepheid Variables Pulsate Because They Contain a Layer That Alternately