Space, pulsars and neutron stars. Neutron Star Universe Pulsars
A pulsar can be seen at the center of the M82 galaxy (pink)
Explore pulsars and neutron stars Universe: description and characteristics with photo and video, structure, rotation, density, composition, mass, temperature, search.
Pulsars
Pulsars are spherical compact objects, the dimensions of which do not go beyond the boundaries of a large city. Surprisingly, with such a volume, they surpass the solar one in massiveness. They are used to study extreme states of matter, detect planets outside 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 out for a pulsar in the sky, it seems like an ordinary twinkling star, following a certain rhythm. In fact, their light does not flicker or pulse, and they do not appear as stars.
The pulsar produces two persistent narrow beams of light in opposite directions. The flickering effect is created due to the fact that they rotate (lighthouse principle). At this point, the beam hits the Earth and then turns again. Why is this happening? The fact is that the light beam of a pulsar usually does not coincide with its axis of rotation.
If the blinking is created by rotation, then the speed of the pulses reflects that at which the pulsar rotates. A total of 2,000 pulsars have been found, most of which make one revolution per second. But there are about 200 objects that manage to make a hundred revolutions in the same time. The fastest ones are called milliseconds because their number of revolutions per second is equal to 700.
Pulsars cannot be considered stars, at least "alive". They are more like neutron stars that form 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 the mass is twice that of the sun. To give you an idea, a piece of such an object the size of a sugar cube would weigh 1 billion tons. That is, something weighing Everest is placed in your hand! There is more truth dense object- black hole. The most massive reaches 2.04 solar masses.
Pulsars have strong magnetic fields that are 100 million to 1 quadrillion times stronger than Earth's. In order for a neutron star to start emitting light like a pulsar, it must have the correct intensity ratio magnetic field and 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 for a pulsar is one rotation per second. The fastest accelerate to hundreds of revolutions per second and are called millisecond. The rotation process occurs because the stars from which they formed also rotated. But to get to this speed, you need an additional source.
Researchers believe that millisecond pulsars were formed by stealing energy from a neighbor. You can notice the presence of foreign matter, which increases the speed of rotation. And this is not good for the affected companion, which one day may be completely absorbed by the pulsar. Such systems are called black widows (after the dangerous species of spider).
Pulsars are capable of emitting light in several wavelengths (from radio to gamma rays). But how do they do it? Scientists have yet to find a definitive answer. It is believed that a separate mechanism is responsible for each wavelength. Beacon-like beams are made up of radio waves. They are bright and narrow and resemble coherent light, where particles form a focused beam.
The faster the rotation, the weaker the magnetic field. But the speed of rotation is enough for them to emit the same bright rays as the slow ones.
During rotation, the magnetic field creates an electric field, which is able to bring charged particles into a mobile state ( electricity). The area above the surface where the magnetic field dominates is called the magnetosphere. Here, charged particles are accelerated to incredibly high speeds due to the strong electric field. With each acceleration, they emit light. It is displayed in the optical and X-ray range.
What about gamma rays? Research suggests that their source must 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 weak compared to other objects, so you have to scan the entire sky and gradually these objects fall into the lens. Most of it was found using the Parkes Observatory in Australia. A lot of new data will be available from the Square Kilometer Antenna Array (SKA) launching in 2018.
In 2008, the GLAST telescope was launched, which found 2050 gamma-ray pulsars, of which 93 were millisecond. This telescope is incredibly useful because it scans the entire sky, while others only highlight small areas along the plane.
Finding different wavelengths can be problematic. The fact is that radio waves are incredibly powerful, but they may simply not fall into the telescope lens. But gamma rays spread over most of the sky, but are inferior in brightness.
Scientists now know about 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.
Use of pulsars
Pulsars are not just amazing space objects, but also useful tools. The emitted light can tell a lot about internal processes. That is, researchers are able to understand the physics of neutron stars. In these objects, the pressure is so high that the behavior of matter is different from the usual. The strange filling of neutron stars is called "nuclear paste".
Pulsars bring many benefits due to the accuracy 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 orbited a pulsar.
Do not forget that pulsars continue to move during the “blinking”, which means that you can use them 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 disturbed by gravitational waves. This was noticed in February 2016.
Pulsar graveyards
Gradually, all pulsars slow down. The radiation is powered by a magnetic field created by rotation. As a result, it also loses its power and stops sending beams. Scientists brought special feature where you can still detect gamma rays ahead of radio waves. As soon as the pulsar falls below, it is written off in the graveyard of pulsars.
If the pulsar was formed from the remnants of a supernova, then it has a huge energy reserve and a fast rotation speed. Examples include the young object PSR B0531+21. In this phase, it can stay 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 companion nearby. Then it will pull out its material and increase the speed of rotation. Such changes can occur at any time, so the pulsar is able to revive. Such a contact is called a low-mass X-ray binary system. The oldest pulsars are millisecond. Some are billions of years old.
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 closer.
When a star explodes, 4-8 times more massive than the Sun, a core with a high density remains, which continues to collapse. Gravity pushes so hard on the material that it causes protons and electrons to coalesce to appear as neutrons. This is how a high-density neutron star is born.
These massive objects are capable of reaching a diameter of only 20 km. To give you an idea of density, just one spoonful 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 an impulse that causes the neutron star to rotate, reaching several revolutions per second. Although they can accelerate up to 43,000 times per minute.
Boundary layers near compact objects
Astrophysicist Valery Suleimanov on the origin 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 ways to study the depths:
When a neutron star is part of a binary system where a supernova exploded, the picture looks even more impressive. If the second star was inferior in massiveness to the Sun, then it pulls the mass of the companion into the “Roche petal”. This is a spherical cloud of matter that makes revolutions around a neutron star. If the satellite was 10 times larger than the solar mass, then the mass transfer is also adjusted, but not as stable. The material flows along the magnetic poles, heats up and X-ray pulsations are created.
By 2010, 1800 pulsars had been found using radio detection and 70 through gamma rays. Some specimens even noticed planets.
Types of neutron stars
In some representatives of neutron stars, jets of material flow almost at the speed of light. When they fly past us, they flash like a beacon. Because of this, they are called pulsars.
Pulsars were discovered quite by accident in the mid-1960s. This happened during observations using a radio telescope, which was originally designed to study various flickering sources in the uncharted depths of space. What are these space objects?
Discovery of pulsars by British researchers
A group of scientists - Joslyn Bell, Anthony Huis and others - conducted research at the University of Cambridge. These pulses came at intervals of 0.3 seconds, and their frequency was 81.5 MHz. Then astronomers did not yet think about what a pulsar really is and what its nature is. The first thing they noticed was the amazing periodicity of the "messages" they discovered. After all, ordinary flickering occurred in a chaotic mode. Among scientists, there was even an assumption that these signals are evidence of trying to reach out to humanity. extraterrestrial civilization. To designate them, the name LGM was introduced - this English abbreviation meant little green men ("little green men"). Researchers began to make serious attempts to decipher the mysterious "code", and eminent decoders from all over the planet were involved for this. However, their attempts were unsuccessful.
Over the next three years, astronomers discovered 3 more similar sources. And then scientists understood what a pulsar is. It turned out to be another object of the Universe, which has nothing to do with alien civilizations. It was then that pulsars got their name. For their discovery, scientist Anthony Hewish was awarded Nobel Prize in physics.
What are neutron stars?
But despite the fact that this discovery happened quite a long time ago, many are still interested in the answer to the question "what is a pulsar." This is not surprising, because not everyone can boast that astronomy was taught at the highest level at his school or university. We answer the question: a pulsar is a neutron star that is formed after a supernova explosion occurs. And so, the constancy of the pulsation, which surprised at the time, can be easily explained - the reason for it is the stability of the rotation of these neutron stars.
In astronomy, pulsars are denoted by a four-digit number. Moreover, the first two digits of the name indicate hours, and the next two - minutes, in which the right ascension of the impulse occurs. And in front of the numbers, two Latin letters are placed, in which the place of discovery is encoded. The very first of all discovered pulsars was named CP 1919 (or "Cambridge Pulsar").
Quasars
What are pulsars and quasars? We have already figured out that pulsars are the most powerful radio sources, the radiation of which is concentrated in individual pulses of a certain frequency. Quasars are also one of the most interesting objects in the entire universe. They are also extremely bright - surpassing in their power the total radiation strength of galaxies, which are similar to Milky Way. Quasars have been discovered by astronomers as high redshift objects. According to one of the widespread theories, quasars are galaxies at the initial stage of their development, inside of which there is
The brightest pulsar in history
One of the most famous such objects in the universe is the pulsar in the Crab Nebula. This discovery shows that the pulsar is one of the most amazing objects in the entire universe.
The explosion of a neutron star in the current Crab Nebula was so powerful that it cannot even fit into the modern theory of astrophysics. In 1054 a.d. e. a new star shone in the sky, which today is called SN 1054. Its explosion was observed even in the daytime, which was evidenced in the historical chronicles of China and the Arab countries. Interestingly, Europe did not notice this explosion - then society was so absorbed in the proceedings between the Pope and his legate, Cardinal Humbert, that not a single scientist of that time recorded this explosion in his works. A few centuries later, a new nebula was discovered at the site of this explosion, later called the Crab Nebula. To its discoverer, William Parsons, for some reason, in its form, it resembled a crab.
And in 1968, the pulsar PSR B0531 + 21 was first discovered, and it was this pulsar that was the first of all that scientists identified with the remnants of a supernova. The source of the pulsation, more strictly speaking, is not the star itself, but the so-called secondary plasma, which is formed in the magnetic field of a star rotating at a frantic speed. The frequency of rotation of the Crab Nebula pulsar is 30 times per second.
A discovery that does not fit into the framework of modern theories
But this pulsar is amazing not only for its brightness and frequency. PSR B0531+21 was recently found to emit radioactive rays in a range that exceeds the 100 billion volt mark. This number is millions of times higher than the radiation used in medical equipment, and it is also ten times higher than the value described in the current theory of gamma rays. Martin Schroeder, an American astronomer, puts it this way: “If just two years ago you had asked any astrophysicist the question of whether this kind of radiation could be detected, you would have received a resounding no. There is simply no such theory, in which the fact that we have discovered can fit in. ”
What are pulsars and how they formed: the mystery of astronomy
Thanks to the study of the Crab Nebula pulsar, scientists have an idea about the nature of these mysterious objects in space. Now you can more or less clearly imagine what a pulsar is. Their occurrence is explained by the fact that at the final stage of their evolution, some stars explode and flare up with a huge firework - a supernova is born. From ordinary stars, they are distinguished by the power of the flash. In total, about 100 such flares occur in our Galaxy per year. In just a few days, a supernova increases its luminosity by several million times.
Without exception, all nebulae, as well as pulsars, appear at the site of supernova outbursts. However, it is not possible to observe pulsars in all remnants of this type of celestial bodies. This should not confuse astronomers - after all, a pulsar can only be observed if it is located at a certain angle of rotation. In addition, due to their nature, pulsars "live" longer than the nebulae in which they form. Scientists still cannot accurately determine the reasons that cause a cooled and seemingly long-dead star to become a source of powerful radio emission. Despite the abundance of hypotheses, astronomers will have to answer this question in the future.
Pulsars with the shortest rotation period
Probably, those who are wondering what a pulsar is and what is the latest news from astrophysicists about these celestial objects will also be interested in knowing the total number of stars of this kind discovered to date. Today, more than 1,300 pulsars are known to scientists. Moreover, a huge number - about 90% - of these stars pulsate in the range from 0.1 to 1 second. There are even pulsars with even shorter periods - they are called millisecond ones. One of them was discovered by astronomers in 1982 in the constellation Vulpecula. Its rotation period was only 0.00155 seconds. A schematic representation of a pulsar includes an axis of rotation, a magnetic field, and radio waves.
Such short periods of rotation of pulsars served as the main argument in favor of the assumption that, by their nature, they are rotating neutron stars (a pulsar is a synonym for the expression "neutron star"). After all, a celestial body with such a period of rotation must be very dense. Research on these objects is still ongoing. Having learned about what neutron pulsars are, scientists did not stop at previously discovered facts. After all, these stars were truly amazing - their existence could be possible only on the condition that the centrifugal forces that arise as a result of rotation are less than the gravitational forces that bind the substance of the pulsar.
Different types of neutron stars
Later it turned out that pulsars with millisecond rotation periods are not the youngest, but, on the contrary, one of the oldest. And pulsars in this category had the weakest magnetic fields.
There is also a type of neutron star called an X-ray pulsar. These are celestial bodies that emit x-rays. They also belong to the category of neutron stars. However, radio pulsars and X-ray emitting stars operate differently and have different properties. The first pulsar of this kind was discovered in 1972 in
The nature of pulsars
When researchers just started to study what pulsars are, they decided that neutron stars have the same nature and density as the nuclei of atoms. This conclusion was made, since all pulsars are characterized by hard radiation - exactly the same as that which accompanies and nuclear reactions. However, further calculations allowed astronomers to make a different statement. The type of space objects "pulsar" is a celestial body that is similar to giant planets (otherwise called "infrared stars").
Astronomers have studied the sky since time immemorial. However, only with a significant leap in the development of technology, scientists were able to discover objects that previous generations of astronomers did not even have in their imagination. Some of them are quasars and pulsars.
Despite the enormous distances to these objects, scientists managed to study some of their properties. But despite this, they still hide a lot of unsolved secrets.
What are pulsars and quasars
The pulsar, as it turned out, is a neutron star. Its pioneers were E. Huish and his graduate student D. Bell. They were able to detect pulses, which are streams of radiation of a narrow direction, which become visible after certain time intervals, since this effect occurs due to the rotation of neutron stars.
A significant compaction of the star's magnetic field and its very density occurs during its compression. It can be reduced to a size of several tens of kilometers, and at such moments the rotation occurs at an incredibly high speed. This speed in some cases reaches thousandths of a second. This is where electromagnetic radiation waves come from.
Quasars and pulsars can be called the most unusual and mysterious discoveries of astronomy. The surface of a neutron star (pulsar) has less pressure than its center, for this reason neutrons decay into electrons and protons. Electrons are accelerated to incredible speeds due to the presence of a powerful magnetic field. Sometimes this speed reaches the speed of light, resulting in the ejection of electrons from the magnetic poles of the star. Two narrow beams electromagnetic waves– this is exactly what the movement of charged particles looks like. That is, electrons emit radiation in the direction of their direction.
Continuing the enumeration of unusual phenomena associated with neutron stars, their outer layer should be noted. In this sphere, there are spaces in which the core cannot be destroyed due to insufficient density of the substance. The consequence of this is that the densest crust is covered by the formation of a crystalline structure. As a result, stress accumulates and at a certain moment this dense surface begins to crack. Scientists call this phenomenon "starquake".
Pulsars and quasars remain completely unexplored. But if amazing studies have told us about pulsars or the so-called. neutron stars have a lot of new things, quasars keep astronomers in the suspense of the unknown.
The world first learned about quasars in 1960. The discovery said that these are objects with small angular dimensions, which are characterized by high luminosity, and by class they belong to extragalactic objects. Because they have a rather small angular size, for many years it was thought that they were just stars.
The exact number of discovered quasars is unknown, but in 2005, studies were conducted in which there were 195,000 quasars. So far, nothing available to explain about them is known. There are many assumptions, but none of them has any evidence.
Astronomers have found out only that for a time interval of less than 24 hours, their brightness marks sufficient variability. According to these data, one can note their relatively small size of the radiation region, which is comparable to the size solar system. Found quasars exist at a distance of up to 10 billion light years. We managed to see them because of their the highest level luminosity.
The closest such object to our planet is located approximately at around 2 billion light years. Perhaps future research and the latest technologies used in them will provide mankind with new knowledge about the white spots of outer space.
The existence of radio sources in space has been known for quite some time. But such an object emitting fast pulses was recorded for the first time. They appeared like clockwork, once a second. At first they thought that the signal was coming from an orbiting satellite, but this idea was quickly discarded. After several more such objects were found, they were named pulsars due to their rapidly pulsating nature.
Bright pulsars have been found at almost every wavelength of light. Some can actually be seen. Most people tend to confuse pulsars with quasars. But these two objects are completely different. Quasars are objects that produce huge amounts of energy. Most likely, they arose as a result of a huge black hole in the center of a young galaxy. But a pulsar is something else entirely.
Pulsars: The Beacon Factor
In essence, a pulsar is a rapidly rotating neutron star. A neutron star is the highly compacted core of a dead star left over from a supernova explosion. This neutron star has a powerful magnetic field. This magnetic field is about one trillion times stronger than the Earth's magnetic field. The magnetic field causes a neutron star to emit strong radio waves and radioactive particles from its north and south poles. These particles can include various radiations, including visible light.
Graphical model of a pulsar
Pulsars that emit powerful gamma rays are known as gamma ray pulsars. If a neutron star is located with its pole towards the Earth, then we can see radio waves every time as soon as one of the poles falls into our foreshortening. This effect is very similar to the lighthouse effect. To a stationary observer, it seems that the light of a rotating beacon is constantly blinking, then disappearing, then appearing again. In the same way, a pulsar appears to blink as it rotates its poles relative to the Earth. Different pulsars fire at different speeds, depending on the size and mass of the neutron star. Sometimes a pulsar can have a companion. In some cases, he can attract his companion, which makes him rotate even faster. The fastest pulsars can emit more than a hundred pulses per second.
neutron stars
The formation of a pulsar occurs when a massive star dies, having exhausted its fuel reserves. going on big Bang, known as a supernova - the most powerful and brightest event in the universe. Without the counterbalancing force of nuclear fusion, gravity begins to pull stellar masses inwards until they become very compressed. In a pulsar, gravity condenses them until an object is formed, consisting mainly of neutrons packed so tightly that they can no longer exist as ordinary matter.
Diagram of the structure of a neutron star
Physicist Chandrasekhar Subrahmanyan suggested that if the mass of the core of the destroyed star is 1.4 times the mass of the star itself, protons and electrons will combine into neutrons in the neutron star. This number is known today as the Chandrasekhar limit. If this limit is not reached as a result of the destruction of the core, then a white dwarf is formed. If this limit is significantly exceeded, then a black hole may result.
The collapsing star begins to rotate more rapidly, which is known as conservation of momentum in rotation. This process is similar to skaters trying to close their hands together to spin even faster. The result is a rapidly rotating ball of densely packed neutrons inside the iron shell. The extreme forces of gravity make this shell very smooth and shiny. As a result, a neutron star is only about 30-35 km in diameter, while containing most of the mass of the original star from which it was formed. The matter of this neutron star is packed so tightly that a piece of this star the size of a sugar cube would weigh more than 100 million tons on Earth.
Discovery of pulsars and neutron stars
New pulsars are being discovered even today with the help of large radio telescopes. The largest radio telescope in the world is located in Arecibo, Puerto Rico. It has been one of the key tools in the search for pulsars. Several new pulsars have been discovered over the past few years. The pulsar is inside the famous Crab Nebula (M1).
The fastest pulsar, PSR1937 +21, has a pulse period of 1.56 ms or 640 times per second. The strongest pulsar is PSR 0329 +54 with a very slow pulse of only 0.715 seconds. Pulsars such as PSR 1257 +12 have recently been discovered. Scientists believe that planets revolve around them.
