A neutron star is the original core of a very massive star, incredibly compressed and left “naked” without a shell. This happens when this giant star “dies” or simply completes a major stage of evolution. The reason why stars “die” is because they run out of hydrogen, which is necessary for thermonuclear reactions in their cores. Only these processes were able to resist gravity. Without these processes, the core would certainly shrink to its ultimate limit. As it contracts, it gets even hotter. Imagine getting even hotter than nuclear fusion. This causes the star’s shell to expand and eventually collapse. From overheating.
When the famous “dying” Betelgeuse (which weighs between 15 and 17 suns) finally bids us farewell in a massive supernova explosion, i.e., when its overheated and expanded shell is shed, its center will be a neutron Most likely to become a star. And this is an example of something that has already happened. The Crab Nebula, also very well known, is nothing but the remains of a supernova explosion in 1054. And right at the center of this nebula is a neutron star. actually observed.
Not all “burned out” stars leave behind such neutron nuclei. It all depends on the mass. Our sun cannot create neutron stars, nor can it explode as a supernova. Because the sun is too light. Of course, it will expand into a red giant star like Betelgeuse, but its shell will “quietly” peel off without a flare, and the sun’s core will shrink to a white dwarf (a star with a diameter of 2,000 kilometers). And its mass would probably be about 60% of the entire Sun. The core of a star like Betelgeuse probably weighs 1.5 times more than the Sun.Such a mass naturally produces a corresponding gravitational force, which leads to a corresponding collapse. Such a heavy core will collapse to a diameter of about 40 kilometers.
Why is this something called a neutron star compressed to such an insignificant size? Such unimaginable compression has already caused the atoms inside to collapse, creating an extremely dense mass of subatomic particles, mostly neutrons plus protons. Neutron stars have another name: pulsars. In fact, it pulsates like a beacon in space due to the radiation of radio waves. When astrophysicists first discovered this pulsation, they initially thought it was a signal from an extraterrestrial civilization.
And why do they pulsate: they rotate very intensely, while the axis of the star moves and sways violently, it looks like a top. In this case, the neutron star emits radio radiation from its poles. Thus, when we look at it through a telescope, the rotating star constantly either turns its pole towards us or hides it. Accordingly, the radio signal appears and disappears.