A neutron star is the remnant of what was once a very massive star that has reached the end of its life span. When a massive star burns up most of its helium and hydrogen much heavier elements like iron remain. The star collapses and produces a supernova explosion. Afterwards, the remaining core becomes so dense that the protons and electrons within come together and become neutrons, hence, neutron star. It is interesting to note that the death of a star can either end in a black hole or a supernova explosion. Some of these supernova explosions from super giant stars become neutron stars. It is also interesting to note that pulsars, which can sometimes result in the formation of a neutron star, are actually rotating neutron stars!
Neutron stars are extremely dense objects. In fact, a teaspoon of neutron star material would weigh about 1 billion tons. When a super giant star burns itself down to its iron core it collapses and rebounds in on itself. When it collapses it creates particles called neutrinos. These neutrinos cause the neutrons to explode outward, creating the beautiful and spectacular stellar explosions that light up the night sky, even shining brighter than galaxies for short periods of time. The remaining material from Type 2 supernovas can create a neutron stars.
But that's not all there is to a neutron star! Neutron stars which emit such pulses while rotating are called pulsars. Neutron stars rotate extremely rapidly after their creation because of the conservation of angular momentum. Eventually they slow down because their rotating magnetic fields radiate energy. Some become so regular in their pulsating and rotating that they are as reliable as atomic clocks. Sometimes a neutron star will undergo a star quake. A star quake creates a rapid and unexpected increase in rotation. The sun also erupts in what scientists call solar quakes but even so, the solar quakes on our sun are not as lethal or powerful as star quakes on neutron stars. On December 27, 2005 a super-magnetic neutron star called SGR 1806-20 erupted in such a quake on the far side of the Milky Way galaxy. This star released more energy in a 10th of a second than the Sun emits in 100,000 years! Some neutron stars also have their own planets. However, it is doubtful that life could ever exist on a planet revolving around a neutron star. They are radioactive in the extreme.
Neutron stars may pulse because of particle acceleration near the magnetic poles that are not aligned with the rotating axis of the star. These particles produce beams of radio emission that pulse with light and radiation whenever the magnetic pole sweeps past the line of sight. The pulses happen at the same rate as the rotation of the star, so they appear to be periodic.
Different types of Neutron stars:
1. Radio-quiet neutron stars
2. Radio emitting
3. Single pulsars
4. Radio pulsars
6. Binary pulsars
7. X-ray pulsar