What Triggers a Supernova Explosion During a Star's Core Collapse?

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Nuclear fusion in massive stars eventually fails to counteract gravitational pressure, leading to core collapse and a subsequent supernova explosion. This collapse generates a shock wave that ejects the star's outer layers, leaving behind a core fragment, often a neutron star, which can be propelled at high speeds due to asymmetrical explosion dynamics. The Chandrasekhar limit, set at approximately 1.39 solar masses, determines whether a star will become a neutron star or a black hole, with progenitor stars needing to exceed eight solar masses to undergo core collapse. Stars below this limit will instead evolve into white dwarfs after forming a planetary nebula. Understanding these processes is crucial for comprehending stellar evolution and supernova mechanics.
humk
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So at some point nuclear fusion in a star becomes unable to sustain the core against its own gravity pressure, then the core collapses and the surface explodes in supernova explosion. What actually happens when the core collapse that makes the surface explode, and why would the core not explode as well?
 
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Studies suggest core collapse triggers an enormous shock wave that blows off the outer layers of the star. A core fragment is all that remains [typically a neutron star]. This fragment can be 'kicked' at surprising speeds in some cases, probably due to asymmetry in the supernova explosion. While progenitor stars are very massive, the surviving core fragment is typically only a little over one solar mass. The remaining material is released into space.
 
The Chandrasekhar limit is the mass needed to become a Supernova either a Neutron Star or a Black Hole as a remnant.

Mass = 1.39*(Mass of the Sun)* ( 2.765 × 10^30 kg)

Under that limit a Planetary Nebula will form resulting in a White Dwarf.
 
White dwarfs are produced by stars that are not massive enough to evolve into core collapse supernova. It is believed core collapse supernova progenitors must be at least 8 solar masses.
 
Philosophaie said:
The Chandrasekhar limit is the mass needed to become a Supernova either a Neutron Star or a Black Hole as a remnant.

Mass = 1.39*(Mass of the Sun)* ( 2.765 × 10^30 kg)

Under that limit a Planetary Nebula will form resulting in a White Dwarf.

The Chandrasekhar limit only applies to the degenerate core of the star. A star with a core which grows more massive than the Chandrasekhar limit will go supernova and produce a neutron star. A progenitor star whose core will become more massive than 1.4 solar masses is about, as Chronos suggested, 8 solar masses total.
 
The core need not reach the Chandrasekhar limit to become a core collapse candidate, that is merely an upper limit. It need only be massive enough to initiate carbon fusion. Most neutron stars are below the Chandrasekhar mass limit. A few behemoths do, however, exist. They remain a scientific curiosity.
 
humk said:
So at some point nuclear fusion in a star becomes unable to sustain the core against its own gravity pressure, then the core collapses and the surface explodes in supernova explosion. What actually happens when the core collapse that makes the surface explode, and why would the core not explode as well?

I recommend a marvelous article by Hans Bethe and Gerald Brown called http://www.cenbg.in2p3.fr/heberge/EcoleJoliotCurie/coursannee/transparents/SN%20-%20Bethe%20e%20Brown.pdf. It will help you understand what happens both in the core and in the surrounding exterior. Great reading.

http://www.cenbg.in2p3.fr/heberge/EcoleJoliotCurie/coursannee/transparents/SN%20-%20Bethe%20e%20Brown.pdf
 
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