Question

What is happening in a star that is on the main sequence on the Hertzsprung-Russell diagram?

a. The star is generating internal energy by hydrogen fusion, creating helium.

b. The star is generating internal energy by helium fusion, creating carbon.

c. Nuclear reactions have ceased, and the star is simply cooling down.

d. The star is slowly shrinking and heating up as it slides up the main sequence from bottom right to top left in the H-R diagram.

Answer 1

Once a star reaches the main-sequence stage, it generates internal energy through hydrogen fusion, creating helium.

Step-by-step explanation:

Once a star reaches the main-sequence stage of its life, it derives its energy by converting hydrogen into helium through nuclear fusion in its core. This process can maintain the star's equilibrium for a long time, keeping it on the main sequence. So, the correct answer is option a: The star is generating internal energy by hydrogen fusion, creating helium.