Question

a) Explain how a protostar is formed.
b) The mass of a red giant staged star is less than $1.4$ times solar mass. Name the last two stages of that star and explain them.

Answer 1

a) Formation of protostar includes following stages:

• Huge gaseous clouds contract due to gravity, and
• There will be increase in density and pressure. The cloud settles with a spherical mass at the centre of the cloud, forming the hydrogen core.

b) The last two stages of star are as follows:

• White dwarf
• Black dwarf

White dwarf : The star collapses under the action of gravity. The temperature increases and the core develops pressure. It shines due to their high temperature.
Black dwarf : In this stage the star loses its energy ( internal ) and temperature. stopping the nuclear reactions which were taking place.