How are neutron stars discovered

Neutron stars

When the nuclear fuel in the core of a massive star is exhausted, this core collapses under the enormous forces of its own gravity within milliseconds. The released energy breaks off the outer shell of the star, which can be observed as a supernova. Inside, gravity compresses the nucleus so much that even the atoms are destroyed by converting protons and electrons into neutrons and neutrinos. This is the birth of a neutron star, which can be called, somewhat simplified, a gigantic atomic nucleus with a radius of about 12 km and 500,000 Earth masses. In the center of a neutron star, several hundred million tons of matter are compressed to one cubic centimeter. Some of these neutron stars rotate so fast that they can make several hundred revolutions per second. They represent the most extreme form of matter in the observable universe.

Pulsars

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Artist's impression of a pulsar.
Artist's impression of a pulsar.

Pulsars are rapidly rotating neutron stars with a strong magnetic field, which preferentially emit electromagnetic radiation along the poles. If the magnet axis is inclined to the axis of rotation, the neutron star's own rotation creates a “cosmic lighthouse” that flashes at regular intervals. The discovery of the first pulsar was made in 1967 by Jocelyn Bell and Antony Hewish. Since then, pulsars have become one of the most exciting fields of research in modern astrophysics.

population

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Simulation of the distribution of pulsars in the Milky Way galaxy, which was determined with an SKA survey of the entire sky ...
Simulation of the distribution of pulsars in the Milky Way, which can be detected with an SKA survey of the entire sky. There are about 20,000 pulsars; shown here with the spiral arm structure of the Milky Way. The galactic center is in the middle, the sun at coordinates (0.0, 8.5) kpc in the upper half of the picture. [Less]
Simulation of the distribution of pulsars in the Milky Way, which can be detected with an SKA survey of the entire sky. There are about 20,000 pulsars; shown here with the spiral arm structure of the Milky Way. The galactic center is in the middle, the sun at coordinates (0.0, 8.5) kpc in the upper half of the picture.

In recent years it has become clear that the previously known population of radio-loud neutron stars was incomplete. New manifestations of neutron stars have been discovered: In addition to the new class of sporadic ("intermittent") pulsars, the discovery of rotating radio transients (RRATs) led to the realization that there is a new class of neutron stars, which is possibly the number of the known neutron stars in the Milky Way by a factor of 3-4. In addition, the discovery of transient radio signals - e.g. in magnetars - has made it clear that some sources are only visible as radio sources at certain times.

Creation properties

Neutron stars are born in huge Type II supernova explosions, i.e. they mark the end of a mass-rich (more than 8 solar masses) main sequence star and the birth of a neutron star with a mass of 1-4 solar masses. [more]

Development of binary systems

The development of binary star systems plays a central role in modern astrophysics, from the precursor stars of supernova explosions to the sources of gravitational waves, for example collisions between neutron stars and black holes or gamma ray flashes, the most violent and energetic known events in the universe . [more]