What is Pulsar ?

Known as pulsars, these stellar relics get their name because of the way their emissions appear to be “pulsating” out into space.

Gold's model has the neutron star rotating very fast, with its rotation period equal to the interval between pulses; only a neutron star could withstand such rapid rotation without disruption.

Not only are these ancient stellar objects very fascinating and awesome to behold, they are very useful to astronomers as well.

Pulses are thought to be produced by radiation beamed towards the solar system from charged particles moving in a strongly compressed magnetic field near the pulsar.

This is due to the fact that they have regular rotational periods, which produces a very precise internal in its pulses – ranging from milliseconds to seconds.

About 1,000 pulsars are now known. Almost all are within the Milky Way , but several pulsars have been found in the Magellanic Clouds, the nearest external galaxies.

Pulsars are types of neutron stars; the dead relics of massive stars.

Additional support for the neutron star model came in 1987 at the start of the observed outburst of Supernova 1987 in the Large Megellanic Cloud, when bursts of neutrinos were detected simultaneously at two widely separated underground observatories (in Japan and Ohio, USA).

What sets pulsars apart from regular neutron stars is that they’re highly magnetized, and rotating at enormous speeds. Astronomers detect them by the radio pulses they emit at regular intervals.

The theory of supernovae predicts that most of the gravitational energy released during the collapse of a supernova remnant to form a neutron star will be converted to neutrinos. The observed supernova bursts support this theory. The search for a pulsar ar the position of Supernova 1987 continues.

The formation of a pulsar is very similar to the creation of a neutron star. When a massive star with 4 to 8 times the mass of our Sun dies, it detonates as a supernova.

Extremely fast pulsars, which emit pulses at intervals from one to several milliseconds, were discovered in the 1980s. Several of them were found to be members of binary star systems with very short periods of revolution.

The outer layers are blasted off into space, and the inner core contracts down with its gravity.

This has led to speculation that millisecond pulsars are formed by the merging of a neutron star and another star in a binary system, where the transfer of mass and angular momentum onto the neutron star" spins it up."

The gravitational pressure is so strong that it overcomes the bonds that keep atoms apart.

The distances to most pulsars are uncertain. The nearest estimated distance for a pulsar, is about 280 light-years. All other pulsars seem to be considerably more distant.

Electrons and protons are crushed together by gravity to form neutrons.

The gravity on the surface of a neutron star is about 2 x 1011 the force of gravity on Earth.

The Crab Nebula pulsar and the 17 pulsars that have been found in 11 globular clusters have somewhat more reliable distance estimates, but there are thousands and even tens of thousands of light-years from the solar system.

So, the most massive stars detonate as supernovae, and can explode or collapse into black holes.

Eight of the 17 pulsars found in globular clusters are members of binary systems. Thirteen pulsars are now known to be members of binary systems. Estimates of pulsar (neutron star) masses from their orbits so far indicate masses from 1.3 to 1.6 solar masses for neutron stars.

Pulsars in very close binary systems are being studied in an effort to detect relativistic effects in their strong gravitational fields, which can be used to check the predictions of the general theory of relativity.

If they’re less massive, like our Sun, they blast away their outer layers and then slowly cool down as white dwarfs.

The discovery of binary pulsars has increased efforts to detect the gravitational waves predicted by this theory. Finally, the three most reliably established extrasolar planets have been discovered orbiting the pulsar-neutron star PSR 1257+12.

But for stars between 1.4 and 3.2 times the mass of the Sun, they may still become supernovae, but they just don’t have enough mass to make a black hole.