Neutron stars are one of the most fascinating subjects in the universe. Their mass is about 1 to 3 times that of the sun, while they are only about 25 km wide. A small sugar-cube-sized neutron star would way as much as a 700-meter wide iron cube, roughly the mass of Mount Everest!
During a star’s lifetime, two forces keep it in balance: the star’s gravitation and its radiation pressure. In the core of the star, hydrogen is continuously fused into helium. After a long period of time, all the hydrogen is converted into helium; the helium starts fusing into heavier elements. Once a layer of iron is reached, no further conversion is possible. When this happens, the radiation pressure of the star drops, and the star is out of balance.
If the star is a giant star(with a mass between 1 and 3 suns), the outer core of the star collapses at about 70,000km/s into the core due to gravitation, while the outer layer of the star is blown away in a supernova explosion. The electron repulsion inside the atom is overcome and the electrons and protons fuse into neutrons. The core of the former star is left- the neutron star. This core is restricted from further collapse due to the neutron degeneracy pressure.
Neutron Star structure:
The neutron stars’ structures are weird and extreme. The crust is probably made of a hard iron nuclei lattice with electrons flowing in between. As we get closer to the core, we see more of neutrons and less of protons. There is no surety about what lies in the core, but our best guess is a superfluid neutron-degenerate matter. In a way, neutron stars can be compared with giant atom cores. The only difference would be-atom cores are held together by strong inter-particle interactions while neutron stars are held together with gravity.
A Few Properties:
Neutron stars are about 25 km wide, but weight from 1 to 3 times the mass of the sun. Yes, they are super dense! The surface temperature of a neutron star is about 1 million Kelvin, compared to the 5800 Kelvin of the sun. The neutron stars have a magnetic field 8 million times stronger than the Earth’s- atoms bend when they are near it. Neutron stars have a gravitational field so intense that the escape velocity is 40% the speed of light!
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