What is a pulsar: definition, features and interesting facts

Pulsars were discovered quite accidentally in the mid-60s of the twentieth century. This happened during observations using a radio telescope, which was originally intended to study various flickering sources in the unknown depths of the cosmos. What are these cosmic objects?

The discovery of pulsars by British researchers

A group of scientists - Jocelyn Bell, Anthony Hewes and others - conducted research at the University of Cambridge. These pulses were delivered with a periodicity of 0.3 seconds, and their frequency was 81.5 MHz. Then astronomers have not yet thought about what a pulsar really is and what its nature is. The first thing they noticed was the surprising frequency of the "messages" they found. After all, the usual flickering occurred in a chaotic regime. Among scientists, even the assumption arose that these signals are evidence of trying to reach out to humanity extraterrestrial civilization. For their designation was introduced the name LGM - this English abbreviation meant little green men ("little green men"). Researchers began to make serious attempts to decipher the mysterious "code", and for this purpose eminent specialists-decipherers from all over the planet were involved. However, their attempts were unsuccessful.

Over the next three years, astronomers have discovered three other similar sources. And then scientists realized what a pulsar is. He was another object of the universe, no relation to the extraterrestrial civilizations. It was then that the pulsars got their name. For their discovery scientist Anthony Hewish was awarded the Nobel Prize in Physics.

What are neutron stars?

But despite the fact that the discovery of this happened long 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 in his school or university astronomy was taught at the highest level. We answer the question: a pulsar is a neutron star, which is formed after a supernova explosion occurs. And since the constancy of pulsation that surprised in its time can easily be explained - its cause is the stability of rotation of these neutron stars.

In astronomy pulsars are denoted by a four-digit number. And the first two digits of the name denote a clock, and the next two digits - minutes, in which there is a direct ascent of the pulse. And ahead of the numbers are put two Latin letters, in which the place of opening is coded. The very first of all open pulsars was called SR 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 separate impulses of a certain frequency. Quasars are also one of the most interesting objects in the entire universe. They are also extremely bright - superior in their power to the overall strength of the radiation of galaxies, which are similar to the Milky Way. Quasars were discovered by astronomers as objects with a large redshift. According to one of the most common theories, quasars are galaxies at the initial stage of their development, inside of which 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 the neutron star in the current Crab nebula was so powerful that it can not even fit into the modern theory of astrophysics. In the year 1054 n. E. A new star shone in the sky, which nowadays 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. Interestingly, Europe did not notice this explosion - then the society was so absorbed in the proceedings between the Pope and his legate, Cardinal Humber, that no scientist of that time had recorded this explosion in his works. A few centuries later, on the site of this explosion, a new nebula was discovered, later named Crab. Her pioneer, William Parsons, she somehow reminded her in her form of a crab.

And in 1968 for the first time PSR B0531 + 21 pulsar was discovered, and this pulsar was the first one that scientists identified with remnants from a supernova. The source of pulsation, judging more strictly, is not the star itself, but the so-called secondary plasma, which is formed in a magnetic field rotating with a furious velocity of a star. The rotation frequency of the pulsar of the Crab nebula is 30 times per second.

Opening, which does not fit into the framework of modern theories

But this pulsar is amazing not only for its brightness and frequency. It was recently discovered that the 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 used in medical equipment, and it is ten times higher than the value that is described in modern gamma-ray theory. Martin Schroeder, an American astronomer, says this: "If only two years ago you asked any astrophysicist the question of whether such radiation could be detected, you would get an unambiguous no. Such a theory, into which the fact discovered by us can fit, simply does not exist. "

What are pulsars and how they were formed: the mystery of astronomy

Thanks to the research of the pulsar of the Crab Nebula, scientists have an idea of the nature of these mysterious objects of the cosmos. Now you can more or less clearly imagine what a pulsar is. Their emergence is explained by the fact that at the final stage of their evolution some stars explode and flare up with a huge fireworks display - a supernova is born. From ordinary stars they are distinguished by the power of the flash. In total, about 100 such outbreaks occur annually in our Galaxy. In just a few days, the supernova increases the luminosity several million times.

All without exception, nebulae, as well as pulsars appear in place of supernova explosions. However, it is not possible to observe pulsars in all remnants of this type of celestial bodies. This should not confuse astronomy enthusiasts - in fact a pulsar can be observed only if it is located at a certain angle of rotation. In addition, because of their nature, pulsars "live" longer than the nebulae in which they form. Scientists still can not pinpoint the causes that cause the cooled and seemingly long dead star to become the source of the most powerful radio emission. Despite the abundance of hypotheses, astronomers will have to answer this question in the future.

Pulsars with the shortest period of rotation

Probably, those who are wondering about what a pulsar is and what are the latest news from astrophysicists about these celestial objects, it will be interesting to know the total number of stars of this kind open to date. Today, scientists know more than 1,300 pulsars. And a huge number - about 90% - these stars are pulsing in the range of 0.1 to 1 second. There are even pulsars with even smaller periods - they are called millisecond. One of them was discovered by astronomers in 1982 in the constellation Chanterelles. The period of its rotation was only 0.00155 sec. Schematic representation of the pulsar includes an axis of rotation, a magnetic field, and also radio waves.

Such short periods of pulsar rotation served as the main argument in favor of assumptions that by their nature they are rotating neutron stars (the pulsar is synonymous with the expression "neutron star"). After all, a celestial body with such a period of rotation must be very dense. Studies of these objects continue to this day. Learning about what neutron pulsars are, scientists did not dwell on the facts discovered earlier. After all, these stars were truly amazing - their existence could only be possible provided that the centrifugal forces that arise due to 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 of this category had the weakest magnetic fields.

There is also a type of neutron stars, called X-ray pulsars. These are celestial bodies that emit X-rays. They also belong to the category of neutron stars. However, radio pulsars and stars that emit X-rays operate in different ways and have different properties. The first such a pulsar was discovered in 1972 in the constellation Hercules.

Nature of pulsars

When the researchers just started to study what pulsars are, they decided that neutron stars have the same nature and density as the nuclei of atoms. Such a conclusion was made, since all pulsars are characterized by hard radiation - exactly the same as that accompanied by nuclear reactions. However, further calculations allowed astronomers to make another statement. The type of cosmic objects "pulsar" is a heavenly body that is similar to giant planets (otherwise called "infrared stars").