Question

What is stellar evolution? Explain the evolution of a star from its birth up to the red giant stage.

Answer 1

The process from the birth to the death of a star is called stellar evolution.
$\bullet$ Inter steller space contains huge gaseous clouds. These gaseous clouds contracts due to their own gravity.
$\bullet$ The central portion alone accounts for $99$% of the mass of the cloud. The sphere formed at the centre is called Protostar.
$\bullet$ The centre of the protostar pressure and temperature reaches about $10$ million kelvin, some of the hydrogen nucleusfuses to for helium nucleus producing a large amount of energy.
$\bullet$ Due to the producing of enormous amount of energy their will be force acting outwards, which tends to expand the star. Thus the star reaches a steady state.
$\bullet$ When the star reaching steady state it will start giving out steady output energy. As the radiation pressure increases beyond the opposing gravitational pull, the star begins to swell consequently, the surface area will be more. As a result of this, the temperature of the star decreases hence emits light which is low frequency radiation then the star is said to be a red giant.