Introduction

Inhabitants of the Far East saw a bright shining light in the sky on July 4, 1054. A star had exploded and today the remnants of that star or supernova are visible as the Crab nebula.

The Crab nebula, which now has a diameter of fourteen lightyears, is giving off large amounts of a radiation called Rontgen radiation. This Rontgen radiation takes a lot of energy to produce and scientists estimate that all the energy left in the nebula will be exhausted within a year. Despite this prediction, the Crab nebula appears to have had a significant amount of energy which it used to transmit the Rontgen radiation for more than ten centuries. This energy is delivered by a tiny Rontgen source in the Crab nebula, left over from the supernova, called a neutron star.

Rontgen Hot Gases

Neutron stars have about the same mass as our Sun, but this mass is so tightly packed that the sphere that encloses it measures about 10 kilometers in diameter. Inside this sphere, the atoms from the star had been broken down into their components of neutrons, protons and electrons. When this occurs the protons and electrons react and start to form neutrons. Eventually the core of the neutron star where the elementary particles are located become surrounded by a fluid of primarily neutrons. This fluid is covered by an extremely dense crust that is a few hundred meters thick.

The gravitational force at the surface of a neutron star can be billions of times stronger than that of our Sun. Neutron stars also have very strong magnetic fields that can trap gas from nearby stars. When that happens, the gas accelerates in the magnetic atmosphere and then falls freely toward the surface of the star. These gases may even accelerate to as fast as one third of the speed of light! Here the gases are heated up to over 10 million kelvin and emit Rontgen radiation. A great deal of energy is created by this process which allows the neutron star to function as a Rontgen source.

Pulsars

The strong magnetic field of the neutron star run from pole to pole (represented by the green lines). The attracted matter is forced to fall to the poles (represented by the the orange and green regions). This causes small, hot spots on both poles, where Rontgen radiation is generated. This radiation is slowly released in narrow bundles from the poles of the star (represented by the blue region).

If the magnetic poles are not lined up with the rotation axis (the red axis line), the poles rotate sometimes in our line sight and back. Scientists can then see the emitted Rontgen radiation as short flashes which vary depending on the speed the neutron star rotates. The pulses reoccur at small and precise intervals between 1 millisecond and 4 seconds. This source is called a Rontgen pulsar.