In the 60-ies of XX century by accident when monitoring radio telescope, which was designed to explore flickers of cosmic radio sources, Jocelyn bell, Antony hewish and other employees of the University of Cambridge in the UK found a series of periodic pulses with a duration of 0.3 seconds at a frequency of 81.5 MHz, which was repeated surprisingly constant time, through 1,3373011 seconds. It was very unlike the usual chaotic random picture occasional flickers. There was even an assumption about extraterrestrials, who at the Land of their signals.

Therefore, for these signals have introduced the notation LGM (short little green men "little green men"). Made serious attempts to identify any code in the incoming pulse. This proved impossible, though, as the story goes, the case had been brought by the most skilled of encryption technology.

Six months later discovered three more such pulsating radio source. It became apparent that the radiation sources are natural celestial bodies. They are called pulsars.

For the discovery and interpretation of radio pulsars Anthony Hueso was awarded the Nobel prize in physics.

Currently, it is believed that the pulsar is a neutron star formed after the supernova. The constant pulsation is explained by the stability of rotation of neutron stars.

Pulsars was used to define a four-digit number. The first two digits stand for hours, two minutes ascension of the pulsar. Ahead are the two letters indicating the place of opening. The first pulsar was designated CF 1919 - Cambridge pulsar. Now the radio pulsars are designated by letters PSR and more accurate coordinates: right ascension (hour, minutes) and declination (mark, angular degrees and minutes).

Famous pulsar in the crab nebula, was indicated earlier NP 0531; now he indicated PSR J0535+2200 (the letter J indicates that the coordinates are given for the year 2000). Its period is 0,033 S. pulsar Signals coming from the clouds, formed from the remnants of Supernova of 1054, noted in the Japanese and Chinese Chronicles.

The pulsar is identified with a star 16,5m, located in the center of the nebula.

Currently there are more than 1300 radio pulsars. The vast majority (90%) have periods in the range from 0.1 to 1 C. There pulsars with small periods of less than 30 MS, the so-called millisecond pulsars.

At the end of 1982 in the constellation Chanterelles was discovered millisecond pulsar with a period of 0,00155 C. Rotation with such amazingly short period means that the star makes 642 revolutions per second. Very short periods of pulsars was the first and most compelling argument in favor of the interpretation of these objects as a rotating neutron stars. A star with such rapid rotation must be extremely tight. Indeed, its very existence is possible only provided that the centrifugal forces associated with rotation, the less force of gravity, binder stars.

Millisecond pulsars were not the youngest and the oldest. They come from binary systems, where the accretion spins no longer young neutron stars. These pulsars are weak magnetic field.

Now is known not only pulsars, emitting radio frequency energy, - they are called pulsars, and x-ray pulsars.

X-ray pulsars emit a regular pulses of x-rays and have a strong magnetic field. They also represent a neutron star, in which the magnetic field along with the rapid rotation and create a ripple effect, although the fields and work differently in the radio and x-ray pulsars.

X-ray pulsars is a close binary system in which one of the stars is the neutron and the other bright star-giant.

X-ray pulsar in Hercules opened in 1972 with research satellite "Uhuru". He sends pulses with a period 1,24 C. This is the period of rotation of the neutron star. The system has another period. Neutron and "normal" star commit circulation around their common center of mass with a period of 1.7 days. "Normal" star when its orbital motion regularly appears on the line of sight, uniting us and a neutron star, because it protects the time the x-ray source. This is possible when the plane stellar orbits is only a small angle to the line of sight. X-rays stopped for about 6 hours then appears again, and so every 1.7 days.

Long-term observations have allowed to establish one - third - period x-ray pulsar in Hercules: the period is 35 days, of which 11 days source shines, and 24 days there. The reason of this phenomenon is still unknown.

Some of x-ray pulsars substance spills over to the neutron star jet, as in busters (regularly flashing x-ray sources). The star-giant loses substance in the form of stellar wind, similar to the solar wind, only many times strong. Part of the stellar-wind plasma is adjudged to be in the vicinity of the neutron star, where it is captured. However, when approaching the surface of a neutron star charged plasma particles begin to experience the influence of a magnetic field of a neutron star-a pulsar. The magnetic field is able to rebuild the accretion flow and make it a spherical unbalanced directed. Because of this, and there is a ripple effect of the radiation effect of the lighthouse.

Neutron star x-ray pulsars have a very strong magnetic field, reaching the values of 108-109 T that 1011-1012 times greater than the average magnetic field of the Sun.

X-ray pulsars are predominantly in the disk of the Galaxy, where he was recently able to see a blue giants.

If we take the period of the crab nebula pulsar T = 0,033 with, then the corresponding speed W = 2p / T, will be approximately 200 rad/S. inequalities for acceleration ?2 R ?2 / G.

On this basis, we find the lower limit of its density, which is equal to p > 6*1014 kg/m3. This is a very significant density, which is a million times the density of white dwarfs.

Density estimation millisecond pulsar with a period T = 0,00155 with leads to even greater importance: p > 2*1017 kg/m3.

This density is approaching density of matter inside atomic nuclei is equal to p > 2*1018 kg/m3. Such a compact, compressed to such a high degree can only be neutron stars: their density really close to nuclear.

As the Earth, the magnetic axis of the neutron star is tilted to its axis of rotation. Because of this, there is the effect of the lighthouse: a bright spot you can see, it is not seen by the observer. Radiation rapidly rotating neutron star appears to the observer intermittent, pulsating. This effect was predicted theoretically by the Soviet astrophysicist C. F. Shvartsman several years before the discovery of x-ray pulsars. Actually radiation of hot spots is, of course, continuously, but it is not evenly in areas not isotropic, and x-rays from him not directed all the time on us, their beam rotates around the axis of rotation of the neutron star, running on Earth once per period.

Radiation of pulsars is nonthermal nature, in no way connected with heating of a neutron star, with temperature from the thermal processes on its surface. It follows from the analysis of the spectrum of radiation of pulsars.

The pulsar in the crab nebula is the remnant of a supernova of 1054. Its radiation is registered in all ranges of electromagnetic waves from radio waves to gamma rays. Most energy it emits in the field of gamma-rays - 1037 erg/s In x-ray pulsar emits about 1036 erg/S. In the optical range, its capacity is about 200 times less, and radio even hundreds of times smaller. Accept the gamma-flux x-ray region in 5-10 times less. You can verify that neither at what temperature radiation heated body cannot possess such a distribution of power on the spectrum.

Neutron star has a significant magnetic field. Most likely, the field has a dipole character, and its axis is tilted to the axis of rotation of the neutron star. The system of magnetic field lines rotates with huge angular velocity with which rotates itself neutron star. On the surface of the neutron star neutrons can decay into protons and electrons. A strong magnetic field picks charged particles and disperse them up to relativistic velocities. The high energy particles, excavated from the surface of neutron stars and accelerated the strong electric field, create a stream that comes from neutron stars similar to the sun or a stellar wind. Magnetic field drags this thread in rotation together on a neutron star. So around it occurs expanding and rotating magnetosphere. Moving electrons generate electromagnetic waves that radiate narrow rapidly rotating beam. Radiation has bremsstrahlung.