What happens after when a star collapses under its own gravity?
We posted about gravitational collapse of stars which was a brief explanation of how a star collapses and how it remains in equilibrium. As long as it has fuel to burn, outward thermal pressure keeps balancing the gravity. Now, when a star has burned out its fuel supply, the star contracts under the influence of gravity until it reaches a new state of equilibrium. Mainly, the three collapsed equilibrium states are formed depending on the mass of star, that are;
1- White Dwarf
2- Neutron Star
3- Black Hole
White Dwarf
In White Dwarf stars, gravity is balanced out by Electron Degeneracy Pressure. This degeneracy prevents further collapse and the star remains in equilibrium at this stage.
Electron Degeneracy Pressure
Electron Degeneracy Pressure: Right after a star exhausts, gravity kind of squeezes the collapsed star inward. Eventually, this inward force compresses the electrons. Since electrons repel each other as they have same charge. This is because certain number of electrons can fill certain orbitals around nucleus. Hence electrons find no room and eventually they oppose gravity and further collapse is stopped. Forming White Dwarf.
Neutron Star
In this type of collapsed star, the force of gravity is opposed by Neutron Degeneracy Pressure.
Neutron Degeneracy Pressure
Neutron Degeneracy Pressure: Further, if star is massive enough to overcome Electron Degeneracy Pressure, electrons and neutrons combine to form neutrons only. Same thing happens to neutrons, they find no space to move around and again further collapse is stopped by neutron degeneracy pressure.
Black Hole
Gravity overcomes. Now, nothing can prevent a star becoming a Black Hole. Therefore, a star must have a mass greater than 3 solar masses to become a black hole.
Solar Mass
The solar mass is taken as standard unit of mass in astronomy. It is approximately equal to the mass of the Sun, 2×1030 kg and is used to indicate the mass of other stars and stellar objects.
