Pulsars were discovered quite by accident in the mid 60-ies of the twentieth century. This happened during observations using a radio telescope, which was originally designed to study various flickering sources in uncharted depths of space. What are these space objects?
The discovery of pulsars by British researchers
A group of scientists - Jocelyn Bell, Anthony Hughes and others - conducted research at Cambridge University. These pulses arrived at a frequency of 0.3 seconds, and their frequency was 81.5 MHz. Then astronomers have not yet thought about what a pulsar is in reality and what its nature is. The first thing they noticed was the amazing frequency of the "messages" they discovered. After all, ordinary flicker occurred in a chaotic mode. Among scientists, even an assumption arose that these signals are evidence of an extraterrestrial civilization trying to reach humanity. For their designation, 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 decryption specialists from all over the planet were involved. However, their attempts were unsuccessful.
Over the next three years, astronomers discovered 3 more similar sources. And then scientists realized what a pulsar is. He turned out to be another object of the Universe that has nothing to do with alien civilizations. It was then that the pulsars got their name. For their discovery, the scientist Anthony Hewish was awarded the Nobel Prize in Physics.
What are neutron stars?
But despite the fact that this discovery happened 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 at his school or university astronomy was taught at the highest level. We answer the question: a pulsar is a neutron star that forms after a supernova burst. And so the constancy of pulsation that surprised at one time can be easily explained - its reason is the stability of 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, at which the pulse ascends directly. And in front of the numbers are two Latin letters in which the opening is encoded. The very first of all open pulsars was called CP 1919 (or the "Cambridge pulsar").
Quasars
What are pulsars and quasars? We have already figured out that pulsars are powerful radio sources whose radiation 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 - exceeding in their power the total radiation power of galaxies, which are similar to the Milky Way. Quasars were discovered by astronomers as objects with a large redshift. According to one popular theory, quasars are galaxies at the initial stage of their development, inside which there is a supermassive black hole.
The brightest pulsar in history
One of the most famous such objects of 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 could not even fit into the modern theory of astrophysics. In 1054 AD e. a new star shone in the sky, which today is called SN 1054. Its explosion was observed even in the daytime, which was witnessed in the historical chronicles of China and the Arab countries. It is interesting that Europe did not notice this explosion - then society was so absorbed in the proceedings between the pope and his legate, Cardinal Humber, that not a single scientist of that time recorded this explosion in his works. And several centuries later, at the site of this explosion, a new nebula was discovered, which later became known as the Crab-shaped. To her discoverer, William Parsons, for some reason, in her form, she resembled a crab.
And in 1968, the first pulsar PSR B0531 + 21 was discovered, and this pulsar was the first of all that scientists identified with the remnants of a supernova. Judging more strictly, the source of the pulsation is not the star itself, but the so-called secondary plasma, which is formed in a magnetic field of a star rotating at a frantic speed. The rotation frequency of the pulsar of the Crab nebula is 30 times in one 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. It has recently been discovered that PSR B0531 + 21 emits radioactive rays in a range that exceeds the 100 billion volt mark. This number is millions of times greater than the radiation that is used in medical equipment, and it is also ten times higher than the value described in the modern theory of gamma rays. Martin Schroeder, an American astronomer, says this: “If only two years ago you asked any astrophysicist the question of whether this kind of radiation could be detected, you would get a definite no. There is simply no such theory into which the fact that we have discovered can fit into. ”
What are pulsars and how they formed: the mystery of astronomy
Thanks to studies of the pulsar of the Crab nebula, scientists have an idea about the nature of these mysterious objects of space. Now you can more or less clearly imagine what a pulsar is. Their appearance is explained by the fact that at the final stage of their evolution, some stars explode and flash with a huge firework - a supernova is born. They are distinguished from ordinary stars by flash power. In total, about 100 such outbreaks per year occur in our Galaxy. In just a few days, a supernova increases luminosity several million times.
Without exception, all nebulae, as well as pulsars, appear at the site of supernova explosions. However, pulsars cannot be observed in all the remnants of this type of heavenly bodies. This should not confuse astronomy lovers - after all, a pulsar can only be observed if it is located at a certain angle of rotation. In addition, by virtue of their nature, pulsars “live” longer than the nebula 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 have to give an answer to this question in the future.
Pulsars with the shortest rotation period
It is likely that those who are wondering what a pulsar is and what the latest news from astrophysicists about these celestial objects will be interested in knowing the total number of stars of this kind discovered to date. Today, scientists know more than 1,300 pulsars. Moreover, a huge amount - 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. One of them was discovered by astronomers in 1982 in the constellation Chanterelle. The period of its rotation was only 0.00155 seconds. A schematic representation of a pulsar includes an axis of rotation, a magnetic field, and also radio waves.
Such short periods of rotation of the pulsars served as the main argument in favor of the assumption that, by their nature, they are rotating neutron stars (the pulsar is a synonym for the expression "neutron star"). After all, a celestial body with such a period of rotation must be very dense. Investigations of these objects are still ongoing. Learning 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 condition that the centrifugal forces that arise as a result of rotation are less than the gravitational forces that bind the pulsar substance.
Different types of neutron stars
Later it turned out that pulsars with millisecond rotation periods are not the youngest, but, on the contrary, are among the oldest. And pulsars of this category had the weakest magnetic fields.
There is also a type of neutron stars called x-ray pulsars. These are such celestial bodies that emit x-rays. They also belong to the category of neutron stars. However, radio pulsars and stars emitting x-rays act differently and have different properties. For the first time, a pulsar of this kind was discovered in 1972 in the constellation Hercules.
The nature of pulsars
When researchers only began to study what pulsars are, they decided that neutron stars have the same nature and density as atomic nuclei. This conclusion was made, since all pulsars are characterized by hard radiation - exactly the same as nuclear reactions accompany. However, further calculations allowed astronomers to make another statement. The type of cosmic object "pulsar" is a celestial body that is similar to giant planets (otherwise called "infrared stars").