White Dwarf and how it supports itself

A White dwarf is a remnant of a star with very low mass. When a small-sized star ends its life in a supernova (which is one of the brightest explosions because it is visible from earth even if the explosion is hundreds of millions of light years) the star will become a white dwarf. Only the core of the star is the white dwarf. It is estimated that our sun will become a white dwarf in thousands of millions of years.

Let me explain how a white dwarf is formed.

When a small-sized star ends its hydrogen supply to fuse helium, the helium will further fuse into carbon, when this happens, the star will become a super-giant. It needs to become a super-giant because for it to increase its luminosity and cool simultaneously it needs to become a super-giant. Only the outer layers of the star will expand. The core will contract. It is estimated that our sun will become a super-giant in a hundreds of millions of years swallowing the inner planets and the outer planets will not get affected much except that they will become hotter. Maybe Pluto will not be so cold like it is today.

When the star ends its super-giant state, the outer layers will get stripped out from the star leaving the star with a contracted, dense core.

A white dwarf cannot keep its energy supply forever and it has to end its heat and energy supply. It then becomes a black dwarf which is a white dwarf without heat and light energy supply. We cannot detect black dwarfs with our naked eyes because they are black but they have a huge gravitational effect on bodies which are near them which we can observe with the help of telescopes. It is thought that there are no known black dwarfs in the universe because the time it takes for a small- sized star to become a black dwarf is estimated to be longer than the universe.

The Pauli Exclusion Principle tells us why a white dwarf does not collapse even further into a neutron star or a black hole. The Pauli Exclusion Principle states that two electrons moving at a definite speed cannot occupy the same energy states at the same volume. The other electrons move at very fast speeds which causes a pressure that balances the white dwarf from the gravitational pull that is pulling inwards in the star which stops the star to stop collapsing even further to form a neutron star or a black hole depending on the mass of the star. This pressure is known as the electron degeneracy pressure. Neutron stars instead have neutrons which stop the star from collapsing even further to form a black hole.

An Indian graduate, Subrahmanyan Chandrasekhar predicted that the maximum mass a star can be and still remain a white dwarf was 1.4 masses. But, a massive star could also become a white dwarf if it throws out some matter to form a white at its death-line. But how would it know that it had to throw out matter?

Thank you for reading….