I've been on a business trip for the past few days, so I'm too late to update today, so I ask you for leave, please be considerate.

The following is an extension of the materials that interested readers can choose to read.

Description of Supernova Explosion

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How terrifying the supernova (SN) explosion is, look at its absolute magnitude. The smaller it is, the higher the luminosity (the power to release electromagnetic energy).

Briefly talking about the classification, according to the spectral characteristics, it is often divided into type I (no hydrogen absorption line), type II (hydrogen absorption line) SN (silicon absorption line), peak absolute magnitude more than -b SN (no silicon absorption line, helium absorption line) and Ic SN (helium-free, silicon absorption line), peak absolute magnitude up to -18 and so on. The absolute magnitude difference is 1, and the luminosity difference is 2.512 times. The absolute magnitude of the Sun is 4.86, and if you put Ia SN in the position of the Sun, then it is 2.512^{25}=8.9\times 10^{9}times the Sun, 8.9 billion Suns! Type II SN luminosity is generally one magnitude smaller, with a peak absolute magnitude between -16 and -17, which is equivalent to more than a billion suns!

Theoretically, there are not so many classifications of supernova explosions, and according to the type of explosion, there are only thermonuclear explosions and nuclear collapses.

[A: Thermonuclear runaay, the explosion of a C-O degenerate nuclear white dwarf.] 】

Single degenerate model, white dwarf + star. The white dwarf accretes (through the Loch lobe flow and common cladding) of the material of the companion star, and the final mass reaches the Chandrasekhar limit (about 1.4 times the mass of the Sun, or up to 2.8 times the mass of the Sun when the rotation and magnetic field of the white dwarf are taken into account), so that the gravitational pull exceeds the electron degenerate pressure, causing the star to collapse. During the collapse process, half of the gravitational energy is released and half is converted into heat energy, causing the temperature of the star to rise rapidly. When the temperature of a certain area reaches the temperature of carbon and oxygen fusion (about 800 million K), ignition (referring to fusion reaction) triggers an uncontrolled thermonuclear reaction. The reason is positive feedback: the heat transfer of degenerate nuclei is very good, and local heat can quickly conduct the entire star, so the star is isothermal. Fusion reactions are sensitively dependent on temperature (power rate), and as the temperature increases, the reaction rate increases exponentially, resulting in a further increase in temperature. Then, the extremely high temperature brings extremely high thermal pressure, which produces a supersonic propagation of the burning flame, which is reduced and lifted everywhere it goes (in fact, the process is very complicated, such as the ignition location), and the energy released by fusion in a short period of time exceeds the gravitational binding energy, and the result is that the star expands rapidly, and finally forms a planetary nebula with no residue.

Double degenerate model, white dwarf + white dwarf. Specifically, it can be CO white dwarf + He white dwarf, CO white dwarf + CO white dwarf and many other possibilities (depending on initial mass, accretion rate, star wind, etc.). The white dwarf star eventually merges and explodes due to gravitational radiation that carries away the orbital angular momentum; Or if the distance is too close, the massive accretion mass is small, and the massive white dwarf before the merger reaches the Chandrasekhar limit and explodes.

In the thermonuclear explosion model, the supernova releases energy only depending on the mass of the predecessor star. It is conceivable that the energy of the double degenerate model is definitely higher than that of the single degenerate model. In fact, some Ia SNs have been observed to have luminosities of magnitude -21 at magnitude -19! Probably evidence of a double degenerate model.

[B: Core collapse (CCSN)]

It is an explosion in the late evolution of a massive star. A total of four types have been proposed, iron core collapse, electron trapping, pairing instability, and photoinduced dissociation.

1. Iron core collapse, an early supernova model. The nucleus of massive stars synthesizes to iron to form an onion structure. In the center is the iron core, followed by silicon shell, magnesium shell, oxygen shell, carbon shell, helium shell, hydrogen shell, and hydrogen cladding. According to this model, Ib SN is a massive stellar explosion with a hydrogen-free shell and a hydrogen-clad cluster, and Ic SN is a massive stellar explosion with a helium-free shell. The continuous combustion of the silicon shell causes the mass of the iron core to continue to increase (silicon fusion is not to synthesize iron, but silicon is needed to synthesize iron, and iron is synthesized from neutron chains), forming a degenerate iron core. The explosion is that the mass of the iron nucleus exceeds the Chandrasekhar limit, the iron nucleus collapses, the gravitational energy is released, the iron nucleus dissociates into helium, the helium captures electrons, starts the neutronization process, releases a large number of neutrinos, takes away about 99% of the gravitational energy, and the core forms a predecessor neutron star with a radius of about 10km, and the time of these processes is only a few seconds! The outer layer has no time to react. The core forms an iron core, the luminosity decreases, and the thermal pressure of the outer layer decreases, causing the outer layer to collapse.

What happens when the collapsing outer material descends and meets the predecessor neutron star? It is widely believed that the supersonic shock wave that produces the rebound! The shock wave hits outward, taking with it the outer layer of material (the direct burst mechanism), explaining the sharp rise in the photometric curve. However, the problem is not so simple, in the 90s, numerical simulations found that the shock wave finally stopped and could not blow up the outer layer. The bulls are joking, neutrinos may be able to resurrect shockwaves. Well, then considering the role of neutrino flow and shock layer, I didn't expect that a small part of the energy could be transferred to the shock wave, and the shock wave was resurrected (delay burst mechanism).

2. Electron trapping, which occurs in O-Mg nuclei massive stars (8-11 solar masses), only replaces the iron nucleus with an oxygen-magnesium nucleus. The oxygen and gilt nuclei of the degenerate nucleus trap electrons in a dense condition (density of about 10^9g/cm^3), so that the electron degenerate pressure decreases rapidly, so that the core collapses.

The above is a class of burst mechanisms, degenerate cores, whether white dwarfs (which can be considered bare degenerate stellar cores), or iron cores, oxygen magnesium cores. The other type of outbreak mechanism is not a degenerate core. Rather, due to some reason, the thermal pressure of the core drops, and gravitational collapse occurs.

3. The pairing is unstable, occurring in massive stars that are 100 times the mass of the Sun (the upper limit is about 140). Such stars, when the core temperature is billions of Kelvin, high-energy photon pairs are annihilated into electron pairs. The thermal pressure drops rapidly, causing collapse, and the gravitational energy released by the collapse increases the photon energy and maintains the continuous annihilation of the photon pair. Familiar no, positive feedback! Another question is, what is the core? Haha, it's definitely not iron! It could be a giant oxygen nucleus, or even a helium nucleus. Since these nuclei are still capable of fusion, the consequences of collapse cause the core temperature to rise rapidly and the reaction rate to increase at a power rate, resulting in an explosion similar to Ia SN. The star explodes completely, blowing up from the core to the outer layers, and does not form neutron stars or black holes.

4. Photoinduced dissociation, which occurs in massive stars with 200 solar masses or larger, with a core temperature so high that photons can shatter atomic nuclei (10 billion K). After absorbing photons, the nucleus fragments free protons and neutrons (collectively called nucleons). At this point, the core is a pot of proton neutron soup, which almost recreates the situation 1 second after the Big Bang. When the core is fully nucleated, the collapse stops. However, as the energy escapes, the temperature drops, the thermal pressure drops, and the collapse resumes, causing the protons and neutrons to degenerate, at which point the core mass exceeds the upper limit of the neutron star's mass, and the collapse continues, eventually forming a black hole. Whether the spilled energy hits the outer layer in the form of high-energy photons is uncertain, but it may also be a gamma burst: the reason is that the black hole rapidly accretes the matter near the core after formation, accreting a sun-mass of matter in tens of seconds! The movement of partially accreted matter near the axis of rotation of the black hole produces a relativistic jet (jet).

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The above is the internal machine, and if we want to visualize the energy level of a supernova explosion, we can simply make an analogy.

For example, the explosion of the Perseid supernova releases about 6.0*10^37J of energy. The neutrino energy released by the most powerful extreme supernova explosion can reach 1*10^48J. The energy level of a gamma-ray burst in a supernova explosion can reach 1*10^45J.

Well, scientific notation must be thanked, otherwise more than 40 zeros are really hard to count.

So what is the concept?

Our sun, in its 10 billion years of life, can release a total of 1.3*10^44J.

The energy of one second of the sun, calculated according to the energy used by human beings every year is 5*10^20J, which can be used for about 800,000 years.