In a star, what balances the inward crush of gravity?

• A. Outward-moving pressure of nuclear fusion
• B. Magnetic fields
• C. Rotation
• D. Radiation-only pressure

Answer: (A)

In a star, gravity pulling inward is balanced by outward pressure from the hot, glowing interior. Nuclear fusion in the core releases energy that heats the surrounding gas and produces radiation, increasing both the gas pressure and the radiation pressure. This outward push counteracts gravity, keeping the star in a steady state. The option describing outward-moving pressure of nuclear fusion best captures this energy-driven support, since the fusion energy is what powers the pressure that holds the star up. Magnetic fields aren’t the main support, rotation provides only limited, situational help, and radiation-only pressure would leave out the essential gas pressure that also contributes to the balance.