What is a neutron star?
Imagine a small cube, the size of a lump of sugar. It's taken from a neutron star. You will know when you try to lift it and check that it weighs, nothing less, than a hundred million tons. That if you have not discovered it before because of the incomprehensible density of neutrons that it has. Or for its strange color. Or because of the incredible gravitational force that it exerts around it. And is that Neutron stars are extraordinary, in every way. But how are they formed? And because?
When the stars explode
Any star with sufficient mass (and "main sequence"), is capable of becoming a neutron star. But let's not get confused. This does not make the process a bit less extraordinary than it is. Because neutron stars are the densest objects we know in the universe. When a very massive star depletes its nuclear fuel, suddenly, its core can become unstable. The gravity of so much mass strongly attracts all the atoms, which are nothing more than a soup of very hot particles. Since there is no fuel that produces fusion, no force counteracts gravity. Thus, the nucleus becomes more and more dense, to such an extent that electrons and protons "melt" into neutrons.
Neutron stars, also called pulsars, are stellar remnants that have reached the end of their evolutionary life: they are born from the death of a star of between 10 and 30 solar masses. Despite their small size (around 20 kilometers in diameter), neutron stars can boast more mass than the Sun because they are particularly dense.
Gravity could continue to act infinitely. However, the pressure of degeneration, which is a pressure that is due to the quantum nature of the particles, allows the very dense neutron star to form without it collapsing on itself. Instead, a very, very small star forms. For the protons and electrons to come together, the neutron stars have to become very hot. Their nuclei at more than ten high to nine degrees Kelvin produce the photo-integration of the materials that compose them.
When it is reached, the degenerate pressure stops the contraction and the star loses its upper layers in a violent supernova. The process, far from ending, continues then. But the star, due to the photo-integration, is slowly cooling down. For the final phases, almost all the matter that existed in the star has been converted into neutrons. If the nucleus had too large a mass, it is believed, it could collapse and form a black hole. But in the case of the stars, this process stops before, and the degenerated pressure keeps the particles very, very close, but without losing their nature. Thus, the neutron stars remain at the limit of the densest matter that exists in the universe.
When the star finishes contracting and reaches equilibrium, what remains is a neutron star. The neutron star is a very compact and very massive object; It has a mass of a pair of solar masses contained in a sphere of 10 km radius. For example, for the Earth to become a neutron star, it should have a radius of only a few hundred meters! Due to the large mass and small radius they have, the gravity on the surface of a neutron star is enormous.
Around a neutron star
Around the neutron stars, they contain an extremely strong gravitational thrust, much greater than that of the earth. This gravitational force is particularly impressive given the small size of the star. This is a consequence of the relativity enunciated by Einstein and supposes, simply, of a manifestation of the nature of the space-time that surrounds us. In short, to run into something like a neutron star is simply amazing because they are, in themselves, an incredible manifestation of the wonders of the universe. So incredible that we still do not know many of its secrets. Secrets that show how fascinating things can be around us.