Three Ways of Star Evolution Based on Initial Mass

End stages of stars having initial mass less than 8 times the mass of the Sun (M_star < 8 M_Sun)

The outer gaseous envelope, which is thrown out during the formation of a white dwarf, is at the centre

1. Red Giant Stage: Stars in this group expand significantly, increasing their size by 100 to 200 times. During this stage, they are called red giants, named for their reddish colour caused by their cooler temperature.
2. White Dwarf Formation: After the red giant stage, the outer gas layers of the star are thrown into space. The core contracts to a size similar to Earth but with much higher mass, leading to an extremely dense star. The pressure due to electrons balances the gravitational force, making the star stable.
3. Final Stage: The star becomes a white dwarf, a small, hot, and dense star. Its temperature decreases over time, but its size and mass remain unchanged forever. A white dwarf is the end stage of stars in this mass range.

End stages of stars having mass between 8 and 25 times the mass of the Sun (8 M_Sun < M_Star < 25 M_Sun):

A recent picture of the supernova explosion, which was first seen in 1054 A.D

1. Red Giant and Supergiant Stages: These stars expand into red giants and later into supergiants, increasing their size by up to 1000 times.
2. Supernova Explosion: At the end of their evolution, these stars undergo a supernova explosion, a massive and energetic event that can make the star visible even during the daytime.
3. Neutron Star Formation: After the explosion, the core contracts to a size of about 10 km, forming a neutron star. Neutron stars are incredibly dense and are made entirely of neutrons.
4. Final Stage: The pressure of neutrons balances the gravitational force, making the neutron star stable forever. A neutron star is the end stage of stars in this mass range.

End stages of stars having mass larger than 25 times the mass of the Sun (M_star > 25 M_Sun):

1. Red Giant and Supergiant Stages: These stars also pass through the red giant and supergiant stages, just like the stars in the second group.
2. Supernova Explosion: At the end of their evolution, these stars undergo a supernova explosion.
3. Black Hole Formation: After the explosion, the remaining core continues to contract indefinitely because no pressure is strong enough to balance the immense gravitational force. The density and gravitational force become so high that not even light can escape from the star.
4. Final Stage: The star becomes a black hole, an object that absorbs everything around it and cannot be seen directly. Black holes are the end stage of stars with extremely high masses.