What causes the outer shell of a star to expand after it leaves the main sequence?

1 Answer
chandramohanPanakkal
Feb 23, 2016

At end of main sequence most of hydrogen is finished,helium burning stars.

Explanation:

Two forces that keep the star in equilibrium is pressure outwards by fusion and gravity's pull inwards..When hydrogen is finished mass reduce too much,gravity educes so pull inwards is reduced and the pressure push pout to make star a giant..

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