Neutron star, definition and study. A-Z index of Cognitio.

A neutron star is a compact star made of degenerate matter, the predominant component of which is neutrons maintained by gravity.

Gravitational interaction, definition and study. A-Z index of Cognitio.

Gravitational interaction

This is a so-called star degenerate star. It is a small massive celestial body – of a order not exceeding ten kilometers – but having very high density and a mass generally ranging between 1.4 and 3 solar masses.

A neutron star is the result of the gravitational collapse of the core of a massive star, followed by the cessation of nuclear fusion reactions for the exhaustion of light elements inside it, and thus represents the ultimate stage of life of stars with mass very big. Neutrons are constituents of the atomic nucleus and are thus called as electrically neutral. The immense gravitational force, no longer counteracted by the thermal pressure of the nuclear reactions that were active during the life of a star, crushes atomic nuclei between them by contacting the subatomic particles by fusing the electrons with the protons transforming them into neutrons. The matter that forms neutron stars is different from ordinary matter, and not yet fully understood.

Neutron stars have a mass similar to that of the Sun, though their radius is a few dozen kilometers, ie several orders of inferior magnitude.

Sun, definition and study. A-Z index of Cognitio.


An isolated neutron star, with no matter around it, is virtually invisible: its very high temperature gives it a bit of visible radiation, ultraviolet, X and gamma, but due to its mildness the light emitted is very small and , at astronomical distances, not detectable. But if the neutron star has a companion, this can give them mass. Or the neutron star can “feed” from matter in the vicinity, for example, it is going through a gas cloud.

In all these cases the neutron star can manifest itself in various forms:

  • Pulsar: Generic term indicating a neutron star that emits directional radiation impulses that can be detected on Earth thanks to its strong magnetic field and its radiation. They function more or less like a rotating beacon or an atomic clock.
  • X-ray Buster – a neutron star with a small binary companion, from which it extracts matter that falls on its surface. The falling matter acquires enormous energy, and is irregularly visible.
  • Magnetar – a type of soft gamma repeater that has a very powerful magnetic field.

Observing neutron stars is not easy, but researchers have long believed that many things can be learned from their study not only on the Universe, but also on how matter works in extreme conditions. For years, astrophysics have been searching in Space for the fusion of two stars of neutrons, an event that emits a very high amount of energy and leads to a “kilo nova”, an astronomical explosion caused by the collision of two supernatural objects.

Astrophysics, definition and study. A-Z index of Cognitio.


The two stars rotate around each other and approach each other more and more until they collide, in a process that becomes a major source of gravitational waves, ripples in space-time.

Neutron star, definition and study. A-Z index of Cognitio.




To open the video  click on the image, good view from your Alessandro Brizzi.

Neutron star, definition and study. A-Z index of Cognitio.

Neutron star