What are the conditions required for the formation of a neutron star?

A neutron star is formed from the remnants of a supernova explosion of a massive star.

When a massive star exhausts its nuclear fuel, it undergoes a catastrophic collapse, resulting in a supernova explosion. The core of the star collapses under its own gravity, and if the mass is greater than 1.4 times that of the sun (known as the Chandrasekhar limit), it will continue to collapse until all the protons and electrons combine to form neutrons. This process is known as electron capture.

The resulting neutron star is incredibly dense, with a mass of about 1.4 times that of the sun but a radius of only about 10 km. The density of a neutron star is so high that a teaspoon of its material would weigh about a billion tonnes.

In addition to their extreme density, neutron stars also have strong magnetic fields, which can be up to a billion times stronger than that of the Earth. They also rotate rapidly, with some neutron stars spinning hundreds of times per second.

Overall, the formation of a neutron star requires a massive star to undergo a supernova explosion and for the resulting core collapse to continue until all protons and electrons combine to form neutrons. The resulting object is incredibly dense, has a strong magnetic field, and rotates rapidly.