Question

Stars spend about 90% of their lives

a. As protostars

b. Forming planets

c. On the main sequence

d. As red giants

e. As planetary nebula

Answer 1

Stars spend approximately 90% of their lives on the main sequence, where they undergo nuclear fusion converting hydrogen into helium.

Step-by-step explanation:

The answer to the student's question: Stars spend about 90% of their lives on the main sequence. During this phase, stars, including our Sun, convert protons into helium through the process of nuclear fusion, providing a long-lasting source of energy. While protostars are the initial stage, and planetary systems may form around some stars, these occur before and after the main-sequence stage, respectively. Stars evolve off the main sequence to become red giants or supergiants as part of their later life cycle.