Did you know that stars die! When stars run out of hydrogen, the nuclear fusion reactions at their core stop and become unstable and collapse. It is important to note that not all stars collapse the same way. Massive stars explode into a supernova and then collapse into neutron stars, or black holes. We know this because of the work of astrophysicist Subrahmanyan Chandrasekhar. Chandrasekhar was an Indian-born scientist who spent 50 years at the University of Chicago. He is most famous for coming up with the theory that explains the death of the universe’s most massive stars. Before Chandrasekhar, scientists assumed that all stars collapsed into white dwarfs when they died. Chandrasekhar limit is the famous prediction done by Subrahmanyan Chandrasekhar.
What is 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 computation.
The scientific 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☉.
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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, 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 reach a mass level lower than the Chandrasekhar limit.
- Stars that have more mass will be converted into a black holes as the pressure due to the electron degeneration will keep them from collapsing until the density is extremely high. Neutrinos are released when through electrons capturing 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.
What is Chandrasekhar Unit?
Chandrasekhar unit explains the maximum mass of a white dwarf star which is equivalent to 1.44 solar masses. The star turns into a neutron star or a black hole when the limit exceeds.
What is the Chandrasekhar limit for a neutron star?
The maximum Chandrasekhar limit for a neutron star is 3 Msun.
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Frequently Asked Questions – FAQs
What happens if a white dwarf exceeds the Chandrasekhar limit?
If a white dwarf exceeds the Chandrasekhar limit, they, under gravitational collapse, evolve as a stellar remnant similar to a neutron star or a black hole.
What is the significance of the Chandrasekhar limit?
The significance of the Chandrasekhar limit is that it is accepted to be 1.4 times the sun’s mass, such that if the white dwarf is within the limit, they stay as such forever. In contrast, the star that exceeds the limit will experience explosions, turning into a supernova.
State TRUE or FALSE: When a star exceeds the Chandrashekhar Limit, it turns into a neutron star or a black hole.
What would happen if a neutron star hit a black hole?
When a massive celestial body such as a neutron star hits a black hole, there is a production of gravitational waves that ripple through the fabric of space-time. Also, there will be the release of nuclear materials such as gold and platinum along with electromagnetic waves. These electromagnetic waves include light waves and gravitational waves.
Is there a limit to the size of a black hole?
The size of the black hole could be up to 50 billion times the mass of our sun.