Neutron stars are the densest objects known in the universe. They are missed black holes, in the sense that gravity does not reach the no-escape value for the velocity as occurs in black hole, but we know-nothing about what's inside a black hole. Whereas we can study the inside of neutron stars.
This is the Wikipedia concise description of a neutron star:
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich.[1] Except for black holes and some hypothetical objects (e.g. white holes, quark stars, and strange stars), neutron stars are the smallest and densest currently known class of stellar objects.[2] Neutron stars have a rakilometerse order of 10 kilometres (6 mi) and a mass of about 1.4 solar masses.[3] They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.
The compression of matter inside a neutron star is immense. Electrons and protons are transformed into neutrons packed extremely tightly.
The density of a neutron star is estimated in the average to be about 5*10
17 kg/m
3. The density of water is 1*10
3 kg/m
3.
To have an idea, if we scoop a teaspoon (5 milliliters) of a neutron star, the content of the teaspoon would weigh (on earth) 5 trillion kilograms, about 11 trillion pounds, just about the mass of a small mountain.
Neutron stars are extremely smooth since gravity does not allow asperity on them and the surface is extremely hard, billions of times the hardness of steel.
Some neutron stars called magnetars have an extremely intense magnetic field, which causes starquakes with fractures of the hard surface and emission of gamma-ray bursts, visible as huge balls of fire trapped by the magnetic field and causing the effect of a pulsating flashlight.
Neutron stars have been observed to collide in 2017 (LIGO gravitational waves and subsequent direct observations of electromagnetic radiations). Such a cataclysm is called Kilonova, or supernova neutron-burst. During such events it is believed that most heavy elements (gold, platinum, Osmium, and Iridium) are formed by a process called R-process, rapid capture of neutrons.
The numbers are huge, from Wiki:
Current astrophysical models suggest that a single neutron star merger event may have generated between 3 and 13 Earth masses of gold.[31]
Mst
Kilonovae is evidently the way God planned to provide the universe with very heavy elements.
Most of the elements we are composed of, including iron in the blood, are all the result of extreme cataclysmic reactions that occurred during the explosions or collisions of stars. The cosmogenic origin of elements is another fascinating topic, worth of its own thread