A pulsar is a highly magnetrized rotating neutron star. They appear to pulse because they have jets of particles moving almost at the speed of light coming from their magnetic poles. These jets produce powerful beams of light. The magnetic pole is slightly misaligned from the rotational axis line, like the magnetic pole on Earth is not in line with our "true north". Picture holding a flashlight in your hand and rotating your hand around. The beam from the flashlight will appear to pulse as it heads towards you and then it stops as it swings away. We observe the beams of light from pulsars only when they are pointing towards Earth and then they appear to go off as the pulsar's magnetic pole is facing away from Earth. This is called the lighthouse effect. The period of pulses range from 1.4 milliseconds to 8.5 seconds.
Shown below is an artist's concept of a pulsar surrounded by material blown away by the supernova explosion.
Image from http://www.nasaimages.org
I did an earlier post of the Life Cycle of a Star. A neutron star is one possible final phase of a star. It is quite a fascinating object that I thought it deserves its own post.
- Neutron stars are unbelievably, incredibly dense. They have a mass about 1.5 times that of our Sun but with a diameter of about 12.5 miles!
- The density of the star has caused the protons and electrons to combine into neutrons, thus giving the stars their name. One teaspoon of its material would weigh over 5 million tons on Earth.
- The denseness also causes an amazing amount of gravity. The escape velocity from the surface of a neutron stay is about one third the speed of light.
- The massive gravity of the star warps light. If we could look at a neutron star, we would be able to see more than half of the star at a time as shown by the image.
- Neutron stars rotate very quickly, some up to several times per second.