Neutron Stars are one of the most extreme and violent things in the whole universe. First discovered by Jocelyn Bell, a research student at Cambridge University in 1967. Neutron stars are described as giant atomic nuclei often the size of small cities such as new york city but as massive as stars.
Neutron stars are born from one of the most majestic celestial bodies in the whole universe, stars. Stars exist because of a balance, the mass of trillions of tons of hot plasma is being pushed toward the center of the star by gravity squeezing material such as hydrogen with such force nuclei start fuzing making heavier and heavier elements such as helium-4. When these atoms fuze they release energy that pushes against gravity trying to escape but gravity pushes it back down forming this balance. While this balance exists stars are pretty much very stable and there is nothing much to worry about.
Eventually, as millions and billions of years go by, helium in the star will run out causing the star to grow bigger and bigger, burning its helium into carbon and carbon into oxygen before they eventually will turn into white dwarfs.
Finally when the helium in the star is exhausted things really start to get interesting for some moment the balance between energy being released and gravity is broken gravity is so big that the core of the star starts to burn hotter and hotter fusing heavier and heavier elements. Carbon burns into neon in centuries neon to oxygen in 1 year, oxygen into silicon in months, and finally silicon into iron in just one day. As iron can be fixed further the immense amount of gravity being exerted into the core is immense that the core collapses into itself. What’s about to begin is often cool but scary at the same time. Electrons and protons due to the immense amount of force being pushed into them cause them to fuse into neutrons and then are compressed into atomic nuclei. In comparison, a ball of iron the size of the earth is compressed into the size of just a city. Not just the center of the star implodes but also the star pulls the outer layer at 25% the speed of light. This implosion bounces off the core of the star producing a shock wave that catapults the remains of the star into space and this are what we call a supernova explosion which will outshine galaxies for months.
What remains after this crazy trip from a star is a neutron star whose mass is a million times the mass of earth but compacted to a cube 25km wide. Neutron stars are so dense that the mass of all humans on earth would be the same as 1cm^3. Surface temperatures in neutron stars often reach a million degrees celsius. Neutron stars are often the same as planets containing an atmosphere, a core, and a crust. The crust of a neutron star is made of solid iron matter left from the supernova. At the base of the crust, nuclei are compressed so close together they often start to touch making sheets of protons and neutrons which are so dense scientists describe this material as the hardest material in the universe which would technically be indestructible.