Since neutron stars are composed of neutrons and are electrically neutral, why is there a super strong magnetic field?

Someone asked: Since neutron stars are composed of neutral neutrons, why is there a strong magnetic field?

First, let's learn how neutron stars come from. The mass of a star qualified to form such a celestial body must be 8 times larger than that of the sun and 30 to 40 times smaller than that of the sun. After the death of this massive star, it will try its best to come back to the light, bursting out huge energy, dispersing most of its mass back to space, leaving a dense core in the center, which is more than 1.44 to about 3 times the mass of the sun. This core is a neutron star.

How big is this core? Radius 10~20km. Some people always don't believe that neutron stars are that good? Heavy? The mass per cubic centimeter reaches1~ 200 million tons. Just think about it. A ball with a radius of10 ~ 20km concentrates the mass of 1.44 suns. You should know that the mass of the sun is1.9891x1030kg and the radius is 696000km. Break your fingers, multiply the mass of the sun by 1.44, and then divide it by the volume of a ball with a radius of 10km, and the density will not come out.

The photo above shows the Crab Nebula, which is 6300 light years away. It is the remnant of a supernova that broke out in 1054, with a neutron star and a pulsar at its center.

Several extreme characteristics of neutron stars. Neutron stars are characterized by high density, ultra-fast rotation speed, ultra-high temperature and ultra-high pressure.

The rotation of neutron stars mainly inherits the angular momentum of protostars, which is a bit like dancing ballet on ice. When an athlete tightens his body, the slow rotation will become faster. The radius of the protostar is hundreds of thousands or even millions of kilometers, which is reduced to 10 kilometers, so it rotates much faster. The fastest millisecond pulsar, such as the neutron star with code name J 1739-285, has a rotation speed of 1 122 rpm; The neutron star PSR0535-69, with the highest known rotation speed, has a rotation speed as high as 1968 revolutions per second.

When the neutron star was first formed, the temperature could reach 10 12k, which is trillions of kelvin, while the surface temperature of the sun was only 6,000 k, and the center temperature was only150,000 k. The temperature of the neutron star was hundreds of millions of times higher than that of the sun. As time goes on, the temperature of neutron star passes through a? Uka？ After 10000 years, the center temperature will drop to10000 k, and the surface temperature will drop to10000 k.

The neutron star pressure reaches 10 28 earth sea level, which is 1 trillion times higher than the earth sea level, 3 trillion times higher than the earth center pressure at about 3 million sea levels, and 300 billion times higher than the sun center pressure of 300 billion.

Because of the extreme characteristics of neutron stars, it is afraid of black holes, and any celestial body near it will be eaten by it, let alone artificial celestial bodies, so it is impossible for humans to observe neutron stars at close range. The surface escape velocity of neutron stars reaches half the speed of light, that is, 15000 km per second. If a person is caught by the gravity of a neutron star and falls on it, the speed will reach half of the speed of light, and the energy generated by the impact will reach 200 million tons of TNT explosion power, which is equivalent to the simultaneous explosion power of four world's largest nuclear bombs "tsar bomba", or more than 15000 Hiroshima atomic bombs.

However, this force may not be able to lift a millimeter wave under the action of the neutron star's huge gravity field.

The other extreme feature is the super magnetic field.

How strong is the magnetic field of neutron stars? Let's compare it. What is the unit of measurement of magnetic field? Gauss? The letter is Gs. The earth's magnetic field of 0.7Gs is enough to resist the invasion of solar wind; Jupiter's magnetic field reaches 14Gs, which is 20 times that of the earth. Generally, the magnetic field in the polar region of the solar magnetic field is very low, only 1Gs, but the solar magnetic field is very active, reaching 1000Gs when the two poles explode, and the magnetic field intensity of the magnetic nodes in the calm region of the solar surface reaches several thousand Gs, but the sunspot explosion magnetic field can reach 4000Gs.

These seemingly strong magnetic fields are completely childish compared with neutron star magnetic fields, so they are used together? Nine Niu Yi hairs? Metaphorically, the stellar magnetic field is greatly overestimated. The magnetic field intensity of neutron stars is at least hundreds of billions of Gs, and the magnetic field intensity of the polar regions on the surface of most pulsars is higher than 65.438+000 billion Gs, even as high as 20 trillion Gs.

Pulsars are a kind of neutron stars, which are rotating neutron stars. It is named because it constantly sends out electromagnetic pulse signals. In fact, neutron stars all rotate, but they are fast and slow. What's the difference between them and pulsars?

This is because the rotation axis of celestial bodies does not coincide with the magnetic axis, and so do neutron stars. In this way, when the neutron star rotates, the energy rays emitted by the magnetic pole will sweep across the space like a lighthouse, and this beam of energy will just sweep to the earth, and it will be regularly and repeatedly swept and accepted by human beings. This neutron star is a pulsar. Because neutron stars are very small, those neutron stars with rotation and energy emission are difficult to be discovered by human beings because their energy signals have not swept the earth. Even if it is found, it is not called a pulsar, but still a neutron star.

Now let's talk about the composition of neutron stars and the problem of uncharged belts. Theoretically, the neutron star is under great pressure, and the electrons outside the atom are pressed into the nucleus, and the negatively charged electrons neutralize the positively charged protons in the nucleus to become neutrons. Add the original neutrons in the nucleus, and the whole planet becomes a planet composed of neutrons, and the density reaches the density of the nucleus.

This theory is ideal, there is nothing wrong, but in fact, the neutron star itself is not a complete neutron ball, but like the earth, it has several different layered structures according to different pressures. Its surface layer is some free electrons that have been crushed by pressure and haven't had time to combine with protons; The second layer is the mixture of nucleus, electron and neutron in the process of combination; The third layer should be all neutrons that have been combined, but under extreme high temperature and pressure, it is superfluid; The fourth floor is the core area of supersolid.

Therefore, the assertion that neutron stars are uncharged is untenable. What's more, even if it is all composed of neutrons, and neutrons are composite particles composed of 1 upper quarks and 2 lower quarks, quarks are charged, 2/3 of the upper quarks are positively charged, and the lower quarks 1/3 are negatively charged.

So it is a misunderstanding that neutron stars are not charged.

So how did the magnetic field of neutron stars come from? Let's first understand how the celestial magnetic field comes from. Although there is no unified understanding of the origin of celestial magnetic field at present, the generator effect is recognized by the scientific community.

As we know, the rotor of the generator cuts the magnetic field lines to generate current, which leads scientists to suggest that there is a similar phenomenon on the earth. Double-shaft generator? The magnetic field produced an effect. The earth has multiple structures, and the density and state of each structure are different. When the earth rotates, the rotation speed of different structures is different, which makes the earth produce stable current and thus produces the earth's magnetic field.

There is a similar theory in the study of solar magnetic field, which is caused by the unbalanced movement of charged materials inside. However, the generation of solar magnetic field also has a fossil source. According to this theory, the existing magnetism of the sun is a legacy of substances formed billions of years ago. This theory actually means that the magnetic field can be obtained or inherited from its predecessor celestial body.

According to these theories, it is not difficult to explain the strong magnetic field of neutron stars.

First, the rotation speed of neutron stars is very fast, reaching hundreds of millions of times that of the earth, and the rotation speed of their layered structures is very different, especially with superconducting superfluid in the middle, which will form a super-strong magnetic field according to the generator effect;

Secondly, neutron stars explode from massive stars, which not only inherit the angular momentum of the previous parent star, but also inherit the magnetism of the parent star.

But a recent study denied the second point, that is, inherited the magnetic field of the parent star. This research was completed by a team of Max Planck Institute for Astrophysics in Munich, Germany. They believe that neutron stars may be extreme magnetic fields generated during their own formation. This process is that in the first few seconds of the collapse of the giant star, the newborn neutron star cools rapidly by emitting neutrinos, which leads to strong internal convection, just like a pot of boiling water tumbling up and down, which leads to the rapid enhancement of the weak magnetic field of the original star.

This theory supports the generator model theory. They simulated this theory through a supercomputer, showing that the initial weak magnetic field of the neutron star has been amplified to 10 16GS, so this speculation is correct.

They believe that if the extremely strong magnetic field is inherited from the protostar, then this extremely strong magnetic field will slow down the rotation speed of the protostar and eventually lead to the rotation speed of the neutron star. But in fact, the rotation speed of neutron stars is very fast, up to 1968 revolutions per second, so this powerful magnetic field can't come from the protostar. However, they did not deny that neutron stars inherited weak magnetic fields from protostars, and it was these weak magnetic fields that were rapidly enhanced by generator theory.

This is the approximate origin of the extremely strong magnetic field of neutron stars. The exact and complete mechanism of the formation of celestial magnetic field is still being explored.

That's it. Welcome to participate in the discussion. Thanks for reading.

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