Objects about which we'll talk in the article, were discovered by accident, although scientists Landau L.D. and Oppenheimer R. predicted their existence back in 1930. We are talking about neutron stars. The characteristics and features of these cosmic luminaries will be discussed in the article.
Neutron and the star of the same name
After the prediction in the 30s of the 20th century about the existence of neutron stars and after the discovery of the neutron (1932), Baade V., together with Zwicky F., in 1933, at a congress of physicists in America, announced the possibility of the formation of an object called neutron star. This is a cosmic body that appears during a supernova explosion.
However, all calculations were only theoretical, since it was not possible to prove such a theory in practice due to the lack of appropriate astronomical equipment and the too small size of the neutron star. But in 1960, X-ray astronomy began to develop. Then, quite unexpectedly, neutron stars were discovered thanks to radio observations.
Opening
The year 1967 was significant in this area. Bell D., as a graduate student of Huish E., was able to discover a cosmic object - a neutron star. This is a body emitting constant radiation of radio wave pulses. The phenomenon was compared to a cosmic radio beacon due to the narrow directionality of the radio beam, which came from a very fast rotating object. The fact is that any other standard star would not be able to maintain its integrity at such a high rotational speed. Only neutron stars are capable of this, among which the first discovered was the pulsar PSR B1919+21.
The fate of massive stars is very different from small ones. In such luminaries there comes a moment when the gas pressure no longer balances the gravitational forces. Such processes lead to the fact that the star begins to shrink (collapse) without limit. With a star mass 1.5-2 times greater than the Sun, collapse will be inevitable. During the compression process, the gas inside the stellar core heats up. At first everything happens very slowly.
Collapse
Reaching a certain temperature, a proton can turn into neutrinos, which immediately leave the star, taking energy with them. The collapse will intensify until all protons turn into neutrinos. This creates a pulsar, or neutron star. This is a collapsing core.
During the formation of a pulsar, the outer shell receives compression energy, which will then be at a speed of more than one thousand km/sec. thrown into space. This creates a shock wave that can lead to new star formation. This one will be billions of times larger than the original. After this process, over a period of one week to a month, the star emits light in quantities exceeding an entire galaxy. Such a celestial body is called a supernova. Its explosion leads to the formation of a nebula. At the center of the nebula is a pulsar, or neutron star. This is the so-called descendant of a star that exploded.
Visualization
In the depths of all space, amazing events take place, among which is the collision of stars. Thanks to a sophisticated mathematical model, NASA scientists were able to visualize the riot of enormous amounts of energy and the degeneration of matter involved in it. An incredibly powerful picture of a cosmic cataclysm plays out before the eyes of observers. The probability that a collision of neutron stars will occur is very high. The meeting of two such luminaries in space begins with their entanglement in gravitational fields. Possessing enormous mass, they exchange hugs, so to speak. Upon collision, a powerful explosion occurs, accompanied by an incredibly powerful release of gamma radiation.
If we consider a neutron star separately, then this is the remnant of a supernova explosion, in which life cycle ends. The mass of a dying star is 8-30 times greater than that of the sun. The universe is often illuminated by supernova explosions. The probability that neutron stars will be found in the universe is quite high.
Meeting
It is interesting that when two stars meet, the development of events cannot be foreseen unambiguously. One of the options describes mathematical model, proposed by NASA scientists from the Space Flight Center. The process begins with two neutron stars located at a distance of approximately 18 km from each other in outer space. By cosmic standards, neutron stars with a mass of 1.5-1.7 times the Sun are considered tiny objects. Their diameter varies within 20 km. Due to this discrepancy between volume and mass, a neutron star has the strongest gravitational and magnetic field. Just imagine: a teaspoon of matter from a neutron star weighs as much as the entire Mount Everest!
Degeneration
The incredibly high gravitational waves of a neutron star around it are the reason why matter cannot exist in the form of individual atoms, which begin to collapse. The matter itself transforms into degenerate neutron matter, in which the structure of the neutrons themselves will not allow the star to pass into a singularity and then into a black hole. If the mass of degenerate matter begins to increase due to addition to it, then gravitational forces will be able to overcome the resistance of neutrons. Then nothing will prevent the destruction of the structure formed as a result of the collision of neutron stellar objects.
Mathematical model
By studying these celestial objects, scientists came to the conclusion that the density of a neutron star is comparable to the density of matter in the nucleus of an atom. Its indicators range from 1015 kg/m³ to 1018 kg/m³. Thus, the independent existence of electrons and protons is impossible. The star's matter practically consists of only neutrons.
The created mathematical model demonstrates how powerful periodic gravitational interactions arising between two neutron stars break through thin shell two stars and are thrown into the space surrounding them, great amount radiation (energy and matter). The process of rapprochement occurs very quickly, literally in a split second. As a result of the collision, a toroidal ring of matter is formed with a newborn black hole in the center.
Important
Modeling such events is important. Thanks to them, scientists were able to understand how a neutron star and a black hole are formed, what happens when stars collide, how supernovae are born and die, and many other processes in outer space. All these events are the source of the most severe chemical elements in the Universe, even heavier than iron, incapable of being formed in any other way. This speaks volumes importance neutron stars throughout the Universe.
The rotation of a celestial object of enormous volume around its axis is amazing. This process causes collapse, but at the same time the mass of the neutron star remains practically the same. If we imagine that the star will continue to contract, then, according to the law of conservation of angular momentum, the angular velocity of rotation of the star will increase to incredible values. If a star needed about 10 days to complete a full revolution, then as a result it will complete the same revolution in 10 milliseconds! These are incredible processes!
Development of collapse
Scientists are studying such processes. Perhaps we will witness new discoveries that still seem fantastic to us! But what could happen if we imagine the development of the collapse further? To make it easier to imagine, let’s take for comparison the neutron star/Earth pair and their gravitational radii. So, with continuous compression, a star can reach a state where neutrons begin to turn into hyperons. Radius celestial body will become so small that in front of us there will be a lump of a superplanetary body with the mass and gravitational field of a star. This can be compared to how if the earth became the size of a ping-pong ball, and the gravitational radius of our luminary, the Sun, were equal to 1 km.
If we imagine that a small lump of stellar matter has the attraction of a huge star, then it is capable of holding an entire planetary system near it. But the density of such a celestial body is too high. Rays of light gradually stop breaking through it, the body seems to go out, it ceases to be visible to the eye. Only the gravitational field does not change, which warns that there is a gravitational hole here.
Discoveries and observations
The first time neutron star mergers were recorded was quite recently: August 17. Two years ago, a black hole merger was detected. It's so an important event in the field of astrophysics, that observations were simultaneously carried out by 70 space observatories. Scientists were able to verify the correctness of the hypotheses about gamma-ray bursts; they were able to observe the synthesis of heavy elements previously described by theorists.
This widespread observation of the gamma-ray burst, gravitational waves and visible light made it possible to determine the region in the sky where the significant event occurred and the galaxy where these stars were located. This is NGC 4993.
Of course, astronomers have been observing short ones for a long time, but until now they could not say for sure about their origin. Behind the main theory was a version of the merger of neutron stars. Now it has been confirmed.
To describe a neutron star using mathematics, scientists turn to the equation of state that relates density to pressure of matter. However, there are a lot of such options, and scientists simply do not know which of the existing ones will be correct. It is hoped that gravitational observations will help resolve this issue. On this moment the signal did not give an unambiguous answer, but it already helps to estimate the shape of the star, depending on the gravitational attraction to the second body (star).
NEUTRON STAR
a star made primarily of neutrons. A neutron is a neutral subatomic particle, one of the main components of matter. The hypothesis about the existence of neutron stars was put forward by astronomers W. Baade and F. Zwicky immediately after the discovery of the neutron in 1932. But this hypothesis was confirmed by observations only after the discovery of pulsars in 1967.
see also PULSAR. Neutron stars are formed as a result of the gravitational collapse of normal stars with masses several times greater than the Sun. The density of a neutron star is close to that of atomic nucleus, i.e. 100 million times higher than the density of ordinary matter. Therefore, with its enormous mass, a neutron star has a radius of only approx. 10 km. Due to the small radius of a neutron star, the force of gravity on its surface is extremely high: about 100 billion times higher than on Earth. This star is kept from collapse by the “degeneracy pressure” of dense neutron matter, which does not depend on its temperature. However, if the mass of a neutron star becomes higher than about 2 solar, then the force of gravity will exceed this pressure and the star will not be able to withstand the collapse.
see also GRAVITATIONAL COLLAPSE. Neutron stars have a very strong magnetic field, reaching 10 12-10 13 G on the surface (for comparison: the Earth has about 1 G). Two different types of celestial objects are associated with neutron stars.
Pulsars (radio pulsars). These objects emit pulses of radio waves strictly regularly. The mechanism of radiation is not completely clear, but it is believed that a rotating neutron star emits a radio beam in a direction associated with its magnetic field, the axis of symmetry of which does not coincide with the axis of rotation of the star. Therefore, rotation causes a rotation of the radio beam, which is periodically directed towards the Earth.
X-ray doubles. Pulsating X-ray sources are also associated with neutron stars that are part of a binary system with a massive normal star. In such systems, gas from the surface of a normal star falls onto a neutron star, accelerating to enormous speed. When hitting the surface of a neutron star, the gas releases 10-30% of its rest energy, while during nuclear reactions this figure does not reach 1%. Heated to high temperature The surface of a neutron star becomes a source of X-ray radiation. However, the fall of gas does not occur uniformly over the entire surface: the strong magnetic field of a neutron star captures the falling ionized gas and directs it to the magnetic poles, where it falls, like into a funnel. Therefore, only the polar regions become very hot, and on a rotating star they become sources of X-ray pulses. Radio pulses from such a star are no longer received, since the radio waves are absorbed in the gas surrounding it.
Compound. The density of a neutron star increases with depth. Beneath a layer of atmosphere only a few centimeters thick there is a liquid metal shell several meters thick, and below that there is a solid crust kilometer thick. The substance of the bark resembles ordinary metal, but is much denser. In the outer part of the bark it is mainly iron; With depth, the proportion of neutrons in its composition increases. Where the density reaches approx. 4*10 11 g/cm3, the proportion of neutrons increases so much that some of them are no longer part of the nuclei, but form a continuous medium. There, the substance is like a “sea” of neutrons and electrons, in which the nuclei of atoms are interspersed. And with a density of approx. 2*10 14 g/cm3 (density of the atomic nucleus), individual nuclei disappear altogether and what remains is a continuous neutron “liquid” with an admixture of protons and electrons. It is likely that neutrons and protons behave like a superfluid liquid, similar to liquid helium and superconducting metals in earthly laboratories.
At even higher densities, the most unusual shapes substances. Perhaps neutrons and protons decay into even smaller particles - quarks; It is also possible that many pi-mesons are born, which form the so-called pion condensate.
see also
ELEMENTARY PARTICLES;
SUPERCONDUCTIVITY;
SUPERFLUIDITY.
LITERATURE
Dyson F., Ter Haar D. Neutron stars and pulsars. M., 1973 Lipunov V.M. Astrophysics of neutron stars. M., 1987
Collier's Encyclopedia. - Open Society. 2000 .
See what a "NEUTRON STAR" is in other dictionaries:
NEUTRON STAR, a very small star with high density, consisting of NEUTRONS. Is last stage evolution of many stars. Neutron stars form when a massive star flares up as SUPERNOVA star, exploding their... ... Scientific and technical encyclopedic dictionary
A star whose matter, according to theoretical concepts, consists mainly of neutrons. Neutronization of matter is associated with the gravitational collapse of a star after its nuclear fuel is exhausted. The average density of neutron stars is 2.1017 ... Big Encyclopedic Dictionary
The structure of a neutron star. A neutron star is an astronomical object that is one of the final products ... Wikipedia
A star whose matter, according to theoretical concepts, consists mainly of neutrons. The average density of such a star is Neutron star 2·1017 kg/m3, the average radius is 20 km. Detected by pulsed radio emission, see Pulsars... Astronomical Dictionary
A star whose matter, according to theoretical concepts, consists mainly of neutrons. Neutronization of matter is associated with the gravitational collapse of a star after its nuclear fuel is exhausted. Average density of a neutron star... ... encyclopedic Dictionary
A hydrostatically equilibrium star, in which the swarm consists mainly from neutrons. Formed as a result of the transformation of protons into neutrons under gravitational forces. collapse at the final stages of evolution of fairly massive stars (with a mass several times greater than... ... Natural science. encyclopedic Dictionary
Neutron star- one of the stages of the evolution of stars, when, as a result of gravitational collapse, it is compressed to such small sizes (the radius of the ball is 10-20 km) that electrons are pressed into the nuclei of atoms and neutralize their charge, all the matter of the star becomes... ... The beginnings of modern natural science
Culver's Neutron Star. It was discovered by astronomers from the Pennsylvania State University in the USA and the Canadian McGill University in the constellation Ursa Minor. The star is unusual in its characteristics and is unlike any other... ... Wikipedia
- (English runaway star) a star that moves at an abnormally high speed in relation to the surrounding interstellar medium. The proper motion of such a star is often indicated precisely relative to the stellar association, a member of which... ... Wikipedia
It occurs after a supernova explosion.
This is the twilight of a star's life. Its gravity is so strong that it throws electrons from the orbits of atoms, turning them into neutrons.
When she loses her support internal pressure, it collapses, and this leads to supernova explosion.
The remains of this body become a Neutron Star, with a mass of 1.4 times the mass of the Sun and a radius almost equal to the radius of Manhattan in the United States.
The weight of a piece of sugar with the density of a neutron star is...
If, for example, you take a piece of sugar with a volume of 1 cm3 and imagine that it is made of neutron star matter, then its mass would be approximately one billion tons. This is equal to the mass of approximately 8 thousand aircraft carriers. Small object with incredible density!
The newborn neutron star boasts a high rotation speed. When a massive star turns into a neutron star, its rotation speed changes.
A rotating neutron star is a natural electrical generator. Its rotation creates a powerful magnetic field. This enormous force of magnetism captures electrons and other particles of atoms and sends them deep into the Universe at tremendous speed. High-speed particles tend to emit radiation. The flickering that we observe in pulsar stars is the radiation of these particles.But we notice it only when its radiation is directed in our direction.
The spinning neutron star is a Pulsar, an exotic object created after a Supernova explosion. This is the sunset of her life.
The density of neutron stars is distributed differently. They have bark that is incredibly dense. But the forces inside a neutron star can pierce the crust. And when this happens, the star adjusts its position, which leads to a change in its rotation. This is called: the bark is cracked. An explosion occurs on a neutron star.
Articles
>A pulsar (pink) can be seen at the center of the M82 galaxy.
Explore pulsars and neutron stars The Universe: description and characteristics with photos and videos, structure, rotation, density, composition, mass, temperature, search.
Pulsars
Pulsars are spherical compact objects whose dimensions do not go beyond the boundary big city. The surprising thing is that with such a volume they exceed the solar mass in terms of mass. They are used to study extreme states of matter, detect planets beyond our system, and measure cosmic distances. In addition, they helped find gravitational waves that indicate energetic events, such as supermassive collisions. First discovered in 1967.
What is a pulsar?
If you look for a pulsar in the sky, it appears to be an ordinary twinkling star following a certain rhythm. In fact, their light does not flicker or pulsate, and they do not appear as stars.
The pulsar produces two persistent, narrow beams of light in opposite directions. The flickering effect is created because they rotate (beacon principle). At this moment, the beam hits the Earth and then turns again. Why is this happening? The fact is that the light beam of a pulsar is usually not aligned with its rotation axis.
If the blinking is generated by rotation, then the speed of the pulses reflects the speed at which the pulsar is spinning. A total of 2,000 pulsars were found, most of which rotate once per second. But there are approximately 200 objects that manage to make a hundred revolutions in the same time. The fastest ones are called millisecond ones, because their number of revolutions per second is equal to 700.
Pulsars cannot be considered stars, at least “living”. Rather, they are neutron stars, formed after a massive star runs out of fuel and collapses. As a result, a strong explosion is created - a supernova, and the remaining dense material is transformed into a neutron star.
The diameter of pulsars in the Universe reaches 20-24 km, and their mass is twice that of the Sun. To give you an idea, a piece of such an object the size of a sugar cube will weigh 1 billion tons. That is, something as heavy as Everest fits in your hand! True, there is an even denser object - a black hole. The most massive reaches 2.04 solar masses.
Pulsars have a strong magnetic field that is 100 million to 1 quadrillion times stronger than Earth's. For a neutron star to start emitting light like a pulsar, it must have the right ratio of magnetic field strength and rotation speed. It happens that a beam of radio waves may not pass through the field of view of a ground-based telescope and remain invisible.
Radio pulsars
Astrophysicist Anton Biryukov on the physics of neutron stars, slowing down rotation and the discovery of gravitational waves:
Why do pulsars rotate?
The slowness of a pulsar is one rotation per second. The fastest ones accelerate to hundreds of revolutions per second and are called millisecond. The rotation process occurs because the stars from which they were formed also rotated. But to get to that speed, you need an additional source.
Researchers believe that millisecond pulsars were formed by stealing energy from a neighbor. You may notice the presence of a foreign substance that increases the rotation speed. And that's not a good thing for the injured companion, which could one day be completely consumed by the pulsar. Such systems are called black widows (after dangerous looking spider).
Pulsars are capable of emitting light in several wavelengths (from radio to gamma rays). But how do they do it? Scientists cannot yet find an exact answer. It is believed that a separate mechanism is responsible for each wavelength. Beacon-like beams are made of radio waves. They are bright and narrow and resemble coherent light, where the particles form a focused beam.
The faster the rotation, the weaker the magnetic field. But the rotation speed is enough for them to emit rays as bright as slow ones.
During rotation, the magnetic field creates an electric field, which can bring charged particles into a mobile state (electric current). The area above the surface where the magnetic field dominates is called the magnetosphere. Here charged particles are accelerated incredibly high speeds due to strong electric field. Each time they accelerate, they emit light. It is displayed in optical and x-ray ranges.
What about gamma rays? Research suggests that their source should be sought elsewhere near the pulsar. And they will resemble a fan.
Search for pulsars
Radio telescopes remain the main method for searching for pulsars in space. They are small and faint compared to other objects, so you have to scan the entire sky and gradually these objects get into the lens. Most were found using the Parkes Observatory in Australia. Much new data will be available from the Square Kilometer Array Antenna (SKA) starting in 2018.
In 2008, the GLAST telescope was launched, which found 2050 gamma-ray emitting pulsars, of which 93 were millisecond. This telescope is incredibly useful because it scans the entire sky, while others highlight only small areas along the plane.
Finding different wavelengths can be challenging. The fact is that radio waves are incredibly powerful, but they may simply not fall into the telescope lens. But gamma radiation spreads across more of the sky, but is inferior in brightness.
Scientists now know of the existence of 2,300 pulsars, found through radio waves and 160 through gamma rays. There are also 240 millisecond pulsars, of which 60 produce gamma rays.
Using pulsars
Pulsars are not just amazing space objects, but also useful tools. The light emitted can tell a lot about internal processes. That is, researchers are able to understand the physics of neutron stars. These objects are so high pressure that the behavior of matter differs from the usual. The strange content of neutron stars is called “nuclear paste.”
Pulsars bring many benefits due to the precision of their pulses. Scientists know specific objects and perceive them as cosmic clocks. This is how speculation about the presence of other planets began to appear. In fact, the first exoplanet found was orbiting a pulsar.
Don’t forget that pulsars continue to move while they “blink”, which means they can be used to measure cosmic distances. They were also involved in testing Einstein's theory of relativity, like moments with gravity. But the regularity of the pulsation can be disrupted by gravitational waves. This was noticed in February 2016.
Pulsar Cemeteries
Gradually, all pulsars slow down. The radiation is powered by the magnetic field created by the rotation. As a result, it also loses its power and stops sending beams. Scientists have drawn a special line where gamma rays can still be detected in front of radio waves. As soon as the pulsar falls below, it is written off in the pulsar graveyard.
If a pulsar was formed from supernova remnants, then it has a huge energy reserve and fast speed rotation. Examples include the young object PSR B0531+21. It can remain in this phase for several hundred thousand years, after which it will begin to lose speed. Middle-aged pulsars make up the majority of the population and produce only radio waves.
However, a pulsar can extend its life if there is a satellite nearby. Then it will pull out its material and increase the rotation speed. Such changes can occur at any time, which is why the pulsar is capable of rebirth. Such a contact is called a low-mass X-ray binary system. The oldest pulsars are millisecond ones. Some reach billions of years of age.
Neutron stars
Neutron stars- rather mysterious objects, exceeding the solar mass by 1.4 times. They are born after the explosion of larger stars. Let's get to know these formations better.
When a star 4-8 times more massive than the Sun explodes, a high-density core remains and continues to collapse. Gravity pushes so hard on a material that it causes protons and electrons to fuse together to become neutrons. This is how a high-density neutron star is born.
These massive objects can reach a diameter of only 20 km. To give you an idea of density, just one scoop of neutron star material would weigh a billion tons. The gravity on such an object is 2 billion times stronger than Earth's, and the power is enough for gravitational lensing, allowing scientists to view the back of the star.
The shock from the explosion leaves a pulse that causes the neutron star to spin, reaching several revolutions per second. Although they can accelerate up to 43,000 times per minute.
Boundary layers near compact objects
Astrophysicist Valery Suleymanov on the emergence of accretion disks, stellar wind and matter around neutron stars:
The interior of neutron stars
Astrophysicist Sergei Popov on extreme states of matter, the composition of neutron stars and methods for studying the interior:
When a neutron star acts as part of dual system, where the supernova exploded, the picture looks even more impressive. If the second star is inferior in mass to the Sun, then it pulls the mass of the companion into the “Roche lobe”. This is a spherical cloud of material orbiting a neutron star. If the satellite was 10 times larger than the solar mass, then the mass transfer is also adjusted, but not so stable. The material flows along the magnetic poles, heats up and creates X-ray pulsations.
By 2010, 1,800 pulsars had been found using radio detection and 70 using gamma rays. Some specimens even had planets.
Types of Neutron Stars
Some representatives of neutron stars have jets of material flowing almost at the speed of light. When they fly past us, they flash like the light of a beacon. Because of this, they are called pulsars.
The end product of stellar evolution is called neutron stars. Their size and weight are simply amazing! Having a size of up to 20 km in diameter, but weighing as much as . The density of matter in a neutron star is many times greater than the density of an atomic nucleus. Neutron stars appear during supernova explosions.
Most known neutron stars weigh approximately 1.44 solar masses and is equal to the Chandrasekhar mass limit. But theoretically it is possible that they can have up to 2.5 mass. The heaviest discovered to date weighs 1.88 solar masses, and is called Vele X-1, and the second with a mass of 1.97 solar masses is PSR J1614-2230. With a further increase in density, the star turns into a quark.
The magnetic field of neutron stars is very strong and reaches 10.12 degrees G, the Earth's field is 1G. Since 1990, some neutron stars have been identified as magnetars - these are stars whose magnetic fields go far beyond 10 to 14 degrees of Gauss. At such critical magnetic fields, physics changes, relativistic effects (bending of light by a magnetic field) and polarization of the physical vacuum appear. Neutron stars were predicted and then discovered.
The first assumptions were made by Walter Baade and Fritz Zwicky in 1933, they made the assumption that neutron stars are born as a result of a supernova explosion. According to calculations, the radiation from these stars is very small, it is simply impossible to detect. But in 1967, Huish's graduate student Jocelyn Bell discovered , which emitted regular radio pulses.
Such impulses were obtained as a result of the rapid rotation of the object, but ordinary stars would simply fly apart from such a strong rotation, and therefore they decided that they were neutron stars.
Pulsars in descending order of rotation speed:
The ejector is a radio pulsar. Low rotation speed and strong magnetic field. Such a pulsar has a magnetic field and the star rotates with equal angular velocity. At a certain moment, the linear velocity of the field reaches the speed of light and begins to exceed it. Further, the dipole field cannot exist, and the field strength lines break. Moving along these lines, charged particles reach a cliff and break off, thus they leave the neutron star and can fly away to any distance up to infinity. Therefore, these pulsars are called ejectors (to give away, to eject) - radio pulsars.
Propeller, it no longer has the same rotation speed as the ejector to accelerate particles to post-light speed, so it cannot be a radio pulsar. But its rotation speed is still very high, matter captured by the magnetic field cannot yet fall onto the star, that is, accretion does not occur. Such stars have been studied very poorly, because it is almost impossible to observe them.
The accretor is an X-ray pulsar. The star no longer rotates so quickly and matter begins to fall onto the star, falling along the magnetic field line. When falling on a solid surface near the pole, the substance heats up to tens of millions of degrees, resulting in X-ray radiation. The pulsations occur as a result of the fact that the star is still rotating, and since the area of the fall of matter is only about 100 meters, this spot periodically disappears from view.
