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Why is a red giant star big? | HIX Tutor

<p>When fuel inside is almost finished the fusion reaction push out wards more.But pull to inside is reduced as gravity become less to reduced mass.This make the star to expand outwards and become red giant.</p>

<p>Stars are in equilibrium due to fusion reaction at center pushing outwards and Gravity pulling in wards. When the fuel is almost finished the gravity is  reduced and so pull to inside is less.</p>

Asher Cohen

A red giant star is big because it has exhausted its core hydrogen fuel, causing the core to contract and the outer layers to expand due to increased pressure and temperature.