Question

A star in the main sequence will maintain a constant size

• A. as long as its helium supply holds out.
• B. because its tendency to contract is opposed by the pressure of the hot interior.
• C. until it is devoured by black holes.
• D. provided that gravitational collapse does not overwhelm its photosphere.

Answer 1

Answer: (B)

because its tendency to contract is opposed by the pressure of the hot interior.

All main sequence stars (including the Sun) are in hydrostatic equilibrium. That is, the inward force of gravity, which tends to compress the star, is balanced by the outward force due to the pressure.