Neutron Star

Neutron stars are the Collapsed Core of giant stars that died in a fiery explosion known as a Supernova. After such an outburst, the cores of these former stars compact into an ultra dense object with the mass of the sun packed into a ball the size of a city.

Formation of neutron stars.

Ordinary Stars maintain their spherical shape because the heaving gravity of their gigantic mass tries to pull their gas toward a central point, but is balanced by the energy from nuclear fusion in their cores, which exerts an outward pressure. At the end of their lives, stars that are between four and eight times the Solar mass burn through their available fuel and their internal fusion reactions cease. The stars' outer layers rapidly collapse inward, bouncing off the thick core and then blasting out again as a violent supernova.

But the dense core continues to collapse, generating pressures so high that protons and electrons are squeezed together into neutrons, as well as lightweight particles called neutrinos that escape into the distant universe. The end result is a star whose mass is 90% neutrons, which can't be squeezed any tighter, and therefore the neutron star can't break down any further.

 

A supernova

The supernova that gives rise to a neutron star imparts a great deal of energy to the compact object, causing it to rotate on its axis between 0.1 and 60 times per second, and up to 700 times per second. The formidable magnetic fields of these entities produce high-powered columns of radiation, which can sweep past the Earth like lighthouse beams, creating what's known as a pulsar.

The properties of neutron stars are utterly out of this world — a single teaspoon of neutron-star material would weigh a billion tons. If you were to somehow stand on their surface without dying, you'd experience a force of gravity 2 billion times stronger than what you feel on Earth.

An ordinary neutron star's magnetic field might be trillions of times stronger than Earth's. But some neutron stars have even more extreme magnetic fields, a thousand or more times the average neutron star. This creates an object known as a magnetar. 

Star quakes on the surface of a magnetar — the equivalent of crustal movements on Earth that generate earthquakes — can release tremendous amounts of energy. In one-tenth of a second, a magnetar might produce more energy than the sun has emitted in the last 100,000 years.