Neutron star

What is Neutron Star

The neutron star is the collapsed core of a giant star, which was between 10 to 29 solar masses before falling. Neutron stars are the smallest and most dense stars, not the fictional quark stars and quaint stars. Neutron is less than the radius of the order of 10 kilometers (6.2 miles) in stars and 2.16 solar masses. They are produced by a large star's supernova explosion, which is combined with the collapse of gravity, which compresses the density of the last white dwarf star from the root of the atomic nucleus.

Once created, they do not actively produce heat, and they are quiet over time; However, they can still grow through collision or accretion. Most of the original models of these objects mean that the neutron stars are almost completely neutron (sub-nuclear particles, which do not have a pure electric charge and have slightly larger mass than the proton); Electrons and protons produce neutrons on the condition in the neutron star present in the normal substance. Neutron strings are partially supported against partial support by neutron degeneration pressure, an event described by the poly-exclusion principle, the way white dwarfs are supported against collapse by electron degeneration pressure . However, the pressure of the neutron degeneration is not enough to hold any object beyond the 0.7M rep and the repulsive atomic forces play a bigger role in supporting greater neutron stars. If the mass of the remaining star is more than the Tolman-Oppenheimer-Volcoff border, then it collapses to make a black hole.

The neutron stars that can be seen are very hot and usually the surface temperature is around 600000 K. They are so dense that a normal size matched tissue contains neutron-star material, which weigh about 3 billion tons, the same weight weighs 0.5 cubic kilometers (about 800 meters of a cube with edges) of the Earth. Their magnetic fields are strong like the earth between 108 and 1015 (100 to 1 quadrillion) folds. The gravitational field on the surface of the neutron star is approximately 2 × 1011 (200 billion) times that of the Earth.

As the core of the star collapses, its rotating rate increases as a result of the protection of angular momentum, so the newly formed neutrino stars rotate several hundred times per second. Some neutron stars emit the electromagnetic radiation beam, which makes them recognizable as a pulsar. Indeed, in 1967 Pulsar's discovery by Jocely Bell Bernel was the first observational suggestion in which neutron stars existed. It is believed that the radiation emitted from the pulsar is mainly emitted from the areas near the magnetic poles. If the magnetic pole does not match the rotational axis of the neutron star, then the emission ray will bolt the sky, and when seen from a distance, if the supervisor is somewhere in the beam path, then it will appear as radiation pulses. Coming from a certain point in space (the so-called "Lighthouse effect"). The fastest rotating neutron star is known PSR J1748-2446ad, rotating at 716 times per second  or 43,000 revolutions per second, which gives a linear motion on the surface in the order of 0.24 c (i.e. approx.) Light speed one quarter).

About 100 million neutron stars have been thought of in the Milky Way, a figure which has been achieved by estimating the number of stars that have gone through a supernova explosion. However, most are old and cold, and neutron stars can be easily detected in some cases, just as they are part of the pulsar or binary system. Slow rotating and non-pronged neutron stars are almost undesirable; However, since the detection of the Hubble Space Telescope of RX J185635-3754, some neutron stars that emit only thermal radiation have been detected. Soft gamma repeaters are considered to be a type of neutron star with very strong magnetic fields, known as magnets, or alternatively, fossil-disk neutron stars around them.

Neutron stars can go through the acceleration in the binary system, which usually makes the system bright in X-ray, while the falling objects on the neutron star can produce hotspots that spawn inside and out in the identified X-ray pulsar system. is. In addition, such accretion can "recycle" the old pulsar and potentially generate mass and spin-ups to rotate them very fast while producing the so-called milliscond pulsar. They will continue to develop binary systems, and eventually the partners can become compact objects such as white dwarf or neutron stars, although the other possibilities involve complete destruction of the companion through hijackers or mergers. The merger of binary neutron stars can be a source of short-term gamma-ray burst and can be a strong source of gravitational waves. In 2017, such a phenomenon was carried out a direct detection of gravitational waves (GW170817), and gravitational waves have been detected indirectly in a system where two neutron stars orbiting each other.

How Neutron Stars are Formed 

Any main sequence star having an initial mass of 8 times above the Sun's mass (8 M above) has the ability to produce a neutron star. As the star evolves away from the sequence, subsequent nuclear burning is produces in iron-rich core. When all nuclear fuel has been exhausted in the core, the core should only be supported by degeneration pressure. The shell deposits more than the core of the shell becomes more than the Chandrasekhar boundary. Pressure of electron-degeneration collapses and the core falls further, causing the temperature to exceed 5 × 109 K. At these temperatures, photodicenteration (breakdown of iron nuclei in alpha particles by high energy gamma rays) occurs. As temperatures rise more, electrons and protons make neutrons through freeing from the flood of neutrons and through electron capture. When the density reaches the atomic density of 4 × 1017 kg / m3, then the neutron degeneration stops the compression. The outer envelope outside the star is halted and flows outwards, forming a supernova from the flow of neutrons produced in the form of neutrons. The remaining remains are a neutron star. If the remains have a mass of more than 3 M it, then it becomes collapsed to become a black hole.

As the core of a giant star is compressed during type II supernovae, type IB or type IC supernova, and collapses in the neutron star, it maintains most of its angular momentum. But, because it contains only a small fraction of its parent's radius (and hence its inertia momentarily decreases), a neutron star is formed with very high rotating speed, and then a very long period It slows down in Neutron stars are known to have rotation periods ranging from 1.4 ms to 30 s. The density of the neutron star also gives it very high surface gravity, in which the typical value is 1012 to 1013 m / s2 (more than 1011 times the Earth). One such measure of gravity is that the escape velocity of neutron stars ranges from 100,000 km / sec to 150,000 km / second, i.e. light from third to half the speed. The gravitational force of the neutron star increases the tremendous amount of fluid. The force of its effect destroys the components of the object atoms, presents all cases equally, in most cases, the rest of the neutron star.

Properties of Neutron Star

Mass and temperature of Neutron Star

The neutron star has a mass of at least 1.1 and probably 3 solar masses (M.). The maximum observed mass of the neutron star is approximately 2.01 M☉. But in general, compact stars with less than 1.39 M the (Chandrasekhar border) are white dwarves, while compact stars having a neutron star (though) between 1.4 M☉ and 3 M☉ (Tolman-Oppenheimer-Volkoff border) needed. There is an interval of a tenth of the solar mass where the mass of low-mass neutron stars and high-mass white dwarfs overlap). Between 3m intermedi and 5 M,, fictitious intermediate-mass stars such quark stars and electrocaque stars have been proposed, but no one has been shown in existence. Stellar remnants beyond 10 M overcome will remove the pressure of neutrons degeneration and the gravitational collapse will usually produce a black hole, although the smallest observed mass of a stellar black hole is approximately 5 M☉.

The temperature inside a newly formed neutron star is around 1011 to 1012 kelvin. However, a large number of neutrinos emitted by this leads to so much energy that the temperature of a separate neutron star falls to about 106 kelvin within a few years. At this lower temperature, most of the light generated by a neutron star is in X-ray.

Density and pressure of Neutron Star

The neutron star has the overall density of 3.7 × 1017 to 5.9 × 1017 kg / m3 (2.6 × 1014 to 4.1 × 1014 times the sun's density), which is equal to the estimated density of atomic nucleus of 3 × 1017 kg / m3. . [27] The density of the neutron star varies from approximately 1 × 109 kg / m3 in the crust - with depth as well as grows inside approximately 6 × 1017 or 8 × 1017 kg / m3 (darker than atomic nucleus) . A neutron star is so thick that the size of one teaspoon (5 ml) of its material will be more than 5.5 × 1012 kg, which is approximately 900 times the mass of the Great Pyramid of Giza. In the gravitational field of a neutron star, its weight will be 1.1 × 1025 N, which is about 15 times the weight of the Moon. From internal layer to center the pressure increases from 3.2 × 1031 to 1.6 × 1034 Pa.

Equation of matter at such high density is not well known because the quantum chromodynamics, superconductivity and the similarity of the theoretical difficulties associated with extrusion of possible behavior of quantum chromodynamics, along with empirical difficulties of observing the characteristics of neutrons in such states Due to this. At least hundreds of parsec are far away.

In a neutron star, there are some properties of the atomic nucleus in which the density (within a sequence of magnitude) and the nucleus is made. In popular scientific writing, neutron stars are sometimes described as "huge nuclei". However, in other cases, neutron stars and atomic nuclei are quite different. A nucleus is organized together with strong interaction, while a neutron star is organized together by gravity. The density of a nucleus is identical, while the neutron stars are composed of several layers with different compositions and densities.

Magnetic Field

The strength of the magnetic field on the surface of the neutron wires is c. 104 to 1011 Tesla. These are orders of greater magnitude compared to any other object: For comparison, a continuous 16 T area has been achieved in the laboratory and is enough to apply the living frog due to dynamagnetic levitation. Changes in the powers of the magnetic field is most likely that different types of neutron stars can be separated from their spectra and explain the periodicity of the pulsar.

Neutron stars are known as Magnets, the strongest magnetic fields in the range of 108 to 1011 Tesla, and widely accepted for neutron star type soft gamma repeaters (SGR) and inconsistent X-ray Pulsar (XXP) Hypotheses have become. The magnetic energy density of 108 T area is greater than the mass-energy density of the normal substance. The areas of this strength are capable of polarizing the vacuum at this point that the vacuum becomes bifurcation. Photons can be merged or split into two, and virtual particle-antiparticle pairs are produced. The field electron changes the level of energy and the atoms are forced into thin cylinders. Unlike a simple pulsar, the magnet spin-down can be directly operated by its magnetic field, and the magnetic field is strong, which gives the crust a stress on the point of fracture. Due to the fracture of the crust, the starks are celebrated as the burst of very bright millisecond hard gamma ray. The fireball is trapped by the magnetic field, and when the star rotates, it comes from inside and out, which is seen as a periodic soft gamma repeater (SGR) emission with a duration of 5- and seconds, and which is Lasts for a few minutes.

The origins of strong magnetic fields are still unclear. A hypothesis is to preserve the original magnetic flux during the formation of "flux freezing" or neutron star. If there is a certain magnetic flux on the surface area of an object.

Structure of Neutron Star

The current understanding of the structure of the neutron stars is defined by the current mathematical model, but it may be possible to guess some details through the study of neutron-star oscillations. A study applied on ordinary wires can reveal the internal structure of neutron stars by analyzing the observed spectra of esteroscizmology, stellar oscillations.

Current models indicate that the substance on the surface of the neutron star is made of a simple atomic nucleus, which is crushed in a solid mesh, in which there is a sea of electrons. It is possible that the nucleus on the surface is iron, due to the high binding energy of the nucleus towards iron. It is also possible that heavy elements like iron sink only under the surface, causing light nuclei such as helium and hydrogen. If the surface temperature is more than 106 kelvin (in the case of a young pulsar), then the surface should be liquid rather than solid phase which can be present in cooler neutron stars (temperature <106 kelvin).

The "atmosphere" of the neutron star is mostly hypothesized to be several micrometric thick, and its dynamics are fully controlled by the magnetic field of the neutron star. Faces a solid "crust" below the atmosphere. Due to the highly gravitational field, the crust is extremely rigid and very smooth (maximum surface irregularity ~ 5 mm).

Moving forward, the nucleus faces a growing number of neutrons; Such nuclei burn quickly on the earth, but remains stable by tremendous pressure. As the process is increasing at depth, the neutron drip becomes overwhelming, and the concentration of free neutron increases rapidly. In that area, there are nuclei, free electrons and free neutrons. The nucleus gets rapidly shortened (pressing gravity and strong force) until the core is reached, by definition, where most of the neutrons are present. The expected hierarchy of atomic stage stages in the inner crust is depicted as "nuclear pasta", which has large structures for low pressure and high pressure. The structure of the supermarket substance in the core remains uncertain. A model describes the core as superfluid neutron-degenerate meter (mostly neutrons, with some protons and electrons). More exotic forms of substance are possible, including high-energy onions and cannes, in addition to degenerative bizarre substances (extra-quirky quarks besides extra quarks), neutrons or ultra-dense quark-digdrates.

Gravity and equation of state of Neutron Star

On the surface of the neutron star, the gravitational field is about 2 × 1011 times stronger than Earth, at approximately 2.0 × 1012 m / s2. Such a strong gravitational field acts as a gravitational lens and turns the radiation emitted by the neutron star in such a way that the parts of the invisible rear surface normally appear visible. If the radius of the neutron star is 3GM / c2 or less then the photons can be trapped in a class, thus the entire surface of that neutron star is visible from a single vantage point, as well as below or below 1 The radius distance of the star, with the photoboy below undone.

A fraction of the mass of a star which collapses to form a neutron star, is released into the supernova explosion from which it is formed (E = mc2, by the rule of mass-energy equivalence). Energy comes from the gravitational bond energy of a neutron star.

Therefore, the gravitational force of a specific neutron star is very large. If an object falls below the height of one meter at a neutron star in a radius of 12 kilometers, then it will reach the ground approximately 1400 kilometers per second. However, even before the effect, the tidal force will cause spaghetting, which will break any type of ordinary object into one stream of material.

Due to the large gravity, the time span between a neutron star and the earth is important. For example, for eight years, a neutron can pass on the surface of the star, yet ten years may have passed on earth, and not with its time-spreading effect on its fast moving.

The neutron star relativist states of State describes the relationship of radius versus mass for different models. The most likely radius for any given neutron star mass is bracketed by model AP4 (the smallest radius) and MS2 (the largest radius). The proportion of binding energy mass of BE gravity is equal to the neutron star gravitational mass seen in the radius "R" meter of the kilogram "M" kilogram.

      ${\displaystyle \beta \ =G\,M/R\,{c}^{2}}$

Given current values

${\displaystyle G=6.67408\times 10^{-11}\,{\text{m}}^{3}{\text{kg}}^{-1}{\text{s}}^{-2}}$

${\displaystyle c=2.99792458\times 10^{8}\,{\text{m}}/{\text{s}}}$

${\displaystyle M_{\odot }=1.98855\times 10^{30}\,{\text{kg}}}$

and star masses "M" commonly reported as multiples of one solar mass,

${\displaystyle M_{x}={\frac {M}{M_{\odot }}}}$

then the relativistic fractional binding energy of a neutron star is

${\displaystyle BE={\frac {886.0\,M_{x}}{R_{\left[{\text{in meters}}\right]}-738.3\,M_{x}}}}$

A 2 M_☉ neutron star would not be more compact than 10,970 meters radius (AP4 model). Its mass fraction gravitational binding energy would then be 0.187, −18.7% (exothermic). This is not near 0.6/2 = 0.3, −30%.

State equation for a neutron star is not known yet. It is believed that it is quite different from a white dwarf, whose state equation is a degenerated gas which can be described in close connection with special relativity. However, the increasing effect of general relativity with a neutron star can no longer be ignored. Several equations of the state have been proposed (FPS, UU, APR, L, SLy, and others) and current research is still trying to force theories to make predictions of neutron star substance. This means that the relationship between density and mass is not fully known, and this causes uncertainty in radii projections. For example, the radius of 1.5 M☉ neutron star may be 10.7, 11.1, 12.1 or 15.1 kilometers (for EOS FPS, UU, APR or L), respectively.