I have been on business trips these days, so I don’t have time to update today. I ask everyone for leave and understand.

The following are extended materials, and interested book friends can choose to read them.

"Description of Supernova explosion"

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How terrifying is a supernova (sn) explosion? It depends on its absolute magnitude. The smaller the light, the higher the luminance (electromagnetic energy release power).

Let me briefly talk about the classification. According to the spectral characteristics, it is often divided into two categories: type i (no hydrogen absorption line) and type ii (with hydrogen absorption line).ia sn (with silicon absorption line), the peak absolute magnitude exceeds -19 magnitude.ib sn (with silicon absorption line, with helium absorption line) and ic sn (with helium, silicon absorption line), and the peak absolute magnitude reaches -18 magnitude. The absolute magnitude difference is 1 and the luminosity difference is 2.512 times. The absolute magnitude of the sun is 4.86 magnitude. If ia sn is placed in the position of the sun, then it is 2.512^{25}=8.9\times 10^{9} times, 8.9 billion suns! Type ii sn is generally smaller in luminosity, and the peak absolute magnitude is between -16 and -17, which is equivalent to more than one billion suns!

In theory, supernova explosions do not have so many categories. According to the type of outbreak, there are only thermonuclear explosions and nuclear collapses.

【a: Thermonuclear runaway, the explosion of the degenerated nuclear white dwarf.】

Simple degenerate model, white dwarf + star. White dwarf accretion (through Lochy lining flow, public cladding) matter accompanying star, the final mass reaches the Chandrasekar limit (about 1.4 times the mass of the sun. If the white dwarf rotates and magnetic field factors, it can reach up to 2.8 times the mass of the sun). Therefore, the gravity 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 star temperature to rise rapidly. When the temperature in a certain area reaches the carbon, oxygen fusion temperature (about 800 million k), and ignition (refers to fusion reaction), it triggers an out-of-control thermonuclear reaction.

Because it is positive feedback: the heat transfer properties of the degenerate nucleus are very good, and local heat can quickly conduct the entire star body, so the star body is isothermal. The fusion reaction sensitively depends on the temperature (power rate), the temperature increases, and the reaction rate increases power rate, resulting in further increase in the temperature. Then, extremely high temperatures bring extremely high thermal pressure, producing ultrasonic propagation and combustion flames, which degenerate wherever they go (in fact, the process is very complicated, such as the ignition position). The energy released by fusion in a short time exceeds the gravitational binding energy, and the consequence is that the star body expands rapidly, eventually forming a planetary nebula without any remains.

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 (relying on initial mass, accretion rate, star wind, etc.). White dwarfs eventually merge and explode due to gravitational radiation taking away the orbital angular momentum; or the distance is too close, the accretion of small mass, and the white dwarf with large mass reaches the Chandrasekar limit before the merger.

In the thermonuclear explosion model, the energy released by supernova depends only on the mass of the predecessor star. It can be imagined that the energy of the double degenerate model is definitely higher than the single degenerate model. In fact, people observed that some ia sn luminosity is more than -19, etc., but actually reaches -21, etc.! It may be evidence of the double degenerate model.

【b:core collapse (core collapse,ccsn)】

It is an explosion in the late stage of the evolution of massive stars. People have proposed four types: iron core collapse, electron capture, pairing instability, and photodissociation.

1. The iron core collapses, an early supernova model. The massive star core is synthesized into iron elements to form an onion structure. The center is the iron core, and then the outer part is the silicon shell, magnesium shell, oxygen shell, carbon shell, helium shell, hydrogen shell, and hydrogen cladding. This model believes that ib sn is a hydrogen-free shell, and a large-mass star burst out with hydrogen cladding.

Sn is a massive star burst without helium shell. The continuous combustion of the silicon shell causes the iron core to continue to increase in the mass of the iron core (silicon fusion does not synthesize iron, but silicon is required to synthesize iron, and iron is synthesized by neutron chains), forming a degenerate iron core. The explosion is that the iron core mass exceeds the Chandrasekar limit, the iron core collapses, and the gravitational energy is released. The iron atom nucleus dissociates into helium, helium captures electrons, and starts the neutronization process, releasing a large number of neutrinos, taking away about 99% of the gravitational energy. The core forms the predecessor neutron star with a radius of about 10km. These processes last only a few seconds! The outer layer does not have time to react. The core forms the iron core, and the photometric decreases, and the thermal pressure of the outer layer decreases, causing the outer layer to collapse.

What happens when the collapsed outer material descends and encounters the predecessor neutron star? It is generally believed that a rebounding supersonic shock wave is generated! The shock wave impacts outward, taking away the outer material (direct burst mechanism), explaining the sharp rise in the photometric curve. However, the problem is not that simple. In the 1990s, numerical simulations found that the shock wave finally stopped and could not explode the outer material. Big bulls joked that neutrinos might reactivate the shock wave. Uh, then considering the role of the neutrino flow and the shock wave layer, I didn't expect that a small part of the energy could be transmitted to the shock wave, and the shock wave was revived (delay burst mechanism).

2. Electron capture occurs in a large-mass star of O-mg nuclear (8-11 times the mass of the sun), which only replaces the iron nucleus with an oxygen-magnesium nucleus. The oxygen of the degenerate nucleus, the ox nucleus of the nucleus, captures electrons under dense conditions (density about 10^9g/cm^3), causing the electron degenerate pressure to rapidly decrease, and the core collapses.

The above is a type of burst mechanism, degenerate core, whether it is a white dwarf (which can be regarded as a naked degenerate star core), an iron core, an oxygen-magnesium core. The other burst mechanism is not a degenerate core. However, for some reasons, the thermal pressure of the core drops and gravitational collapse occurs.

3. The pairing is unstable, and occurs at 100 times (upper limit is about 140) of large-mass stars with sun mass. When the core temperature of this type of star is billions of Kelvin, high-energy photon pairs annihilate into electron pairs. The thermal pressure drops rapidly, causing collapse. The gravitational energy released by the collapse increases the photon energy and keeps the photon pairs continuously annihilated. It looks familiar, and positive feedback! Another question, what is the core? Haha, it is definitely not iron anymore! It may be huge oxygen nuclei, or even helium nuclei. Since such nuclei can still fusion, the consequences of collapse cause the core temperature to rise rapidly, and the reaction rate becomes larger by power rate, resulting in an explosion similar to ia sn. The star body completely explodes, and it is blown away from the core to the outer layer, and it will not form neutron stars or black holes.

4. Photodissociation occurs at a massive star with a mass of 200 times the mass of the sun or greater, with a core temperature that is so high that the photon can crush the nucleus (10 billion k). After the nucleus absorbs the photon, free protons and neutrons (collectively known as nucleons). At this time, the core is a pot of proton neutron soup, which almost reproduces the situation after the Big Bang. When all the cores are nucleated, the collapse stops. However, as energy escapes, the temperature drops, the thermal pressure drops, and the collapse reopens.

At first, protons and neutrons degenerate. At this time, the core mass exceeds the upper limit of the neutron star mass, collapse continues, and eventually forms a black hole. The overflowing energy hits the outer layer in the form of high-energy photons. Whether it causes a burst is uncertain, it may also be a gamma burst: the reason is that after the black hole is formed, the matter near the core is rapidly accreted, and a material with the mass of the sun is accumulated within tens of seconds! Part of the accreted material moves to the axis of the rotation of the black hole to produce a relativistic jet (jet).

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The above is an internal machine. If you want to vividly understand the energy level of supernova explosion, we can simply make an analogy.

For example, the energy released by the Perseus supernova explosion is about 6.0*10^37j. The neutrino energy released by the most powerful 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, I have to thank the scientific notation method, otherwise more than 40 zeros will be really difficult to count.

So what is the concept?

Our sun, 10 billion years of career, can release a total of 1.3*10^44j.
Chapter completed!