Chandrasekhar Limit

Chandrasekhar Limit

The utmost mass that a white dwarf star that’s stable can have is known as the Chandrasekhar limit. E.C. Stoner and Willhelm Anderson pointed it out in their papers and termed it after Subrahmanyan Chandrasekhar an Indian astrophysicist who made major independent discoveries on improving the preciseness of the computation. The scientist community ignored the limit at the start as it would legitimize the existence of black holes (technically unrealistic at this turn-off time). Due to the pressure of electron degeneration, the white dwarf stars oppose its gravitational collapse. Chandrasekhar limit is established at a point when the mass at which the pressure from the degeneration of electrons is not able to balance the self-attraction of the gravitational field. The limit that has been established these days is 1.39 M.

The Physics of it

Pauli’s exclusion principle gives rise to a phenomenon of quantum-mechanics termed as Electron degeneracy pressure. Electrons cannot have the same state or the minimum-energy level. This is because they are fermions. A spectrum of energy levels exists and electrons should be distributed throughout them. When the electron gas is compressed, the amount of electrons in a specific volume increases and so does the energy level of the band that has been occupied. Thus, to produce the electron degeneracy pressure, a pressure must be applied for the compression of the electron gas as their energy increases when compressed. Electron capture occurs when that pressure is so great that the electron goes into the nuclei.

Application of Chandrasekhar Limit

When the nuclei of lighter elements fuse into the nuclei of a heavier one the resultant heat is what keeps the core of the star from collapsing. The core will become condensed and hotter when collapsed as the exhaustion of the nuclei will take place. As getting energy through fusion is impossible in the case of iron ions, a dangerous circumstance occurs when iron amasses in the core. If the star is less than 8 solar masses, it will sooner or later get to a mass level lower than the Chandrasekhar limit. Stars that have more mass will be converted into a black hole as the pressure due to the electron degeneration will keep them from collapsing till the density is extremely high. Neutrinos are released when through electron capturing the electrons are captured by the protons. The released neutrinos take away the energy that was created due to the decreasing potential energy (collapse of the core). The energy is around 1046 joules.


Practise This Question

If the power of two lenses and P1 and P2; when they are combined; the effective power is: