How a Neutron Star is Born

A neutron star is created when a massive star collapses under its own gravity during the explosion of a supernova.  A neutron star is the remnant of a high-mass star of about 5-10 solar masses, and is composed of neutrons. The size of a neutron star can be of just 12 km (7 miles) in diameter with the density of an atomic nucleus, and is supported from further collapse by neutron degeneracy pressure. In 1967 Jocelyn Burnell and Antony Hewish were investigating sources of radio emission when they detected very strange signals. These signals of great periodic precision resulted to be originated by a rotating neutron star, now called pulsar.

How a neutron star is created

The creation of a neutron star begins in the core of a massive star. When the energetic explosion of a type II supernova explosion causes the collapse of a high mass star, the electrons combine with the protons, forming neutrons and neutrinos. The neutrinos are blown off into outer space and the collapse of the star only stops when the core has reached the density of an atomic nucleus. At the time when the density is reached, the star ceases to collapse, and there is a sudden halt that produces a shock wave that removes the outer layers of the star. The remaining neutron core is a neutron star.

The very high density attained by the neutron star during its formation also produces a very high surface gravity. Its surface gravity is so high that an object on its surface would require the power of one third the speed of light to be able to escape its force of gravity. An object approaching the surface of a neutron star would be accelerated to tremendous speeds causing a tremendous impact that would destroy all the object´s elemental particles, and melt all its components to the rest of the neutron star.

Neutron star (pulsar)

Due to the compression that the neutron star has been subjected, and the small size it has attained compared to the original size of the massive star, its moment of inertia has been reduce significantly; gaining more angular momentum, therefore at the beginning of its formation, it can spin rapidly between 1.4-30 seconds, emitting electromagnetic radiation. This radiation is emitted in the form of pulses that vary from milliseconds to seconds, depending on the periodicity of rotation of the neutron star. The radio energy is emitted at regular intervals and specific direction into space and the pulses can be detected when they cross the path of the earth.

Pulses of electromagnetic radiation

The beams of light are produced by the rotating energy of the star, which generates an electrical field, and cause the acceleration of protons and electrons at the surface of the star, creating an electromagnetic beam of light at the poles.  In the same way that original angular momentum power intensified as the star compressed, its magnetic field is also many times stronger. Every time a neutron star rotates, a beam of electromagnetic radiation is sent in a path through space. The strong magnetic field and the rapid rotation of the neutron star often help astronomers locate them in the universe.

The rotation of a neutron star slows down gradually as the electromagnetic radiation is emitted. Over time, the rotation of the star stops and so the emission of radiation. It is thought that this may occur in the lapse time of 10-100 million years. At the time, the first signs of a pulsar were detected, astronomers believed them to be originated by extraterrestrials. According to, a neutron star usually forms from stars with between 5-10 solar masses and stars with masses above 10 solar masses usually become a black hole.