Pulsar and Neutron Star, the dead remnants of a dead massive star

Neutron Stars

A Pulsar that does not spin is a plain Neutron Star. A Neutron Star is the remnants of a dead giant star that has finished burning its energy/fuel and exploded in a supernova explosion. A neutron star may only be the size of a city (say 20km), but they are extremely dense and heavy. A teaspoon of a neutron star would weigh over a billion tons. Their weight is because all the neutrons are tightly packed together. Ref: Space

White Dwarf Star are the remnants of low-mass stars like our own star. They do not become Pulsars, but that does not mean they monopolise creating cosmic rays. AE Aquarii has been found to exhibit some Pulsar like characteristics. Its behaviour resembles the Pulsar in Crab Nebular more than other white dwarf stars. AE is a binary star system, so although the main is K Type star, the companion is a White Dwarf star. N.A.S.A.

In an estimated five billion years, our Sun will die, shedding its mass in stellar winds as a planetary nebula. It is too small for the Sun to become a pulsar or a black hole. Before that time, the Sun will have become a red supergiant as the outwards pressure overcomes the inward pressure of gravity. As our star grows, it will "consume" the planets. Which planets it consumes in total is open for debate. By the time the next phase starts, hopefully, humans will have managed to get off this planet, either to Mars or to a planet in another solar system.

A Neutron Star gets its name from what the star consists of neutrons. A neutron is produced when the neutron and electrons are crushed together during the explosion. A star can only become a neutron star when its solar mass is between 1 and 3 solar masses. Anything higher will create a black hole. Neutron stars can not only be found in Pulsars but also Magnetars and at the centres of supernova remnants. Ref: N.A.S.A. The Crab Nebula Supernova Remnant has a Pulsar in the centre.

The below picture shows you the size of a pulsar compared to Manhattan Island, New York City. The image is a screenshot from a video that N.A.S.A. produced on YouTube to explain Pulsars. Clicking on the picture below will take you to the YouTube page.

What is a Pulsar?

Pulsar is the short and most common name for 'Pulsating Star'. An exploding star can also create a planetary nebula. A planetary nebula is what happens when a dying star is not big enough to go supernova. Pulsars are, in short, rotating Neutron Stars. If a pulsar is not spinning, it is not a pulsar and a normal neutron star. Over time, a pulsar will slow down and become just a neutron star. The time it takes to stop spinning can be in the order of millions or billions of years.

Compared to a planet or an asteroid, a Pulsar is incredibly small. It can be nothing bigger than a large city like London or New York. Although they might be as big as a city, their mass could be many million times the mass of the Earth. The reason for the difference is the extreme amount of gravity that is pulling in on itself.

The picture below is from NASA and is an artist's impression of a new kind of Pulsar. The ball at the centre of the Pulsar is the neutron star. The pink is the gamma rays that shoot out from the Pulsar. The blue lines are the magnetic field lines.

Given its name, it is no surprise that the Pulsar will rotate so that the gamma rays will not always fire in the same direction. We can only detect a pulsar when its beams are firing towards us.

Pulsars are not only fast spinning, but they are also fast moving. Pulsars have been spotted moving at speeds of 500 kilometres a second. With that speed, they will be able to escape the gravitational pull of the galaxy that currently orbits and then free-float in space. Not only will there be rogue stars and Planets but also Rogue Pulsars. Manchester University

Pulsars will slow down over time such as the Crab Pulsar. The crab pulser slows down at 38 nanoseconds per day. A nanosecond is 1/1,000,000,000 or a billionth of a second. However, they may slow down, and the degradation in spin is negligible. Any distortion in the spinning could herald something nearby, such as a planet. A planet's immaterial size compared to the object will tug on it and affect the spinning. In comparison, despite our Earth being tiny compared to the Sun, the Earth does influence the Sun, causing it to wobble.

Difference between Characteristic and True Age of a Pulsar

A Pulsar's age cannot be calculated using a formula that uses the neutron star's rotation period and its slowing rate, as that would not give you the true age of the Pulsar. The formula would give you what is called its "Characteristic Age". N.R.A.O.

The True Age of a pulsar is different. It is the real age of the Pulsar. The Crab Pulsar is an often-given example of a pulsar of differing ages. It has a Characteristic Age of 1240 years, but the true age of the Pulsar is about 960 years. The supernova that produced the Pulsar occurred in 1054 A.D. Swinburne

Why do Pulsars spin?

Pulsars spin because the pre-cursors to Neutron stars, the stars also spin. When a star explodes, the explosion's force will increase the object's spinning power. Space. Futurism gives the example of a figure skater spinning faster as curls up using a concept called Angular Momentum. If you watch this YouTube video, it will explain Angular Momentum better than writing words. The fastest spinning neutron star in a pulsar is snappily named PSRJ 1748-2446 and is in the constellation of the archer, Sagittarius.

Discovery of Pulsars

The first pulsars were discovered by Jocelyn Bell Burnell and Doctor Anthony Hewish on November 28th,1967, when they started getting signals from space. Jocelyn did not get the recognition she deserved then but was subsequently recognised later.

The two discoverers thought they'd discovered signals from an alien life form trying to communicate with us. The object they had discovered was code-named LGM1, standing for Little Green Man 1, which has now been disproved. The theory of aliens was discounted when another signal of the same type was found in another part of space. Doctor Anthony Hewish was her doctoral advisor at the time.

The signals were regular and seemed to be artificial rather than natural, which was why they were thought to have been alien signals at one time. Further investigation revealed that it was not artificial. The first Pulsar to be discovered was PSR J1921+2153 in the constellation of Vulpecula.

Gravitational Waves

Discovery of pulsars validated Einstein's Theory of General Relativity. In the theory, it was said that two stars orbiting one another would pull themselves together. As the two stars pulled closer, they would around orbit one another faster and faster, creating gravitational waves when they collided. In the video, Jocelyn says the theory is right, 0.02% because you will never get 100% right. B.B.C.

Although Pulsars are the remnants of a dead star, they have been discovered to have orbiting planets. The planets that orbit pulsars are normally referred to as a Pulsar Planet. When a star goes supernova, it is thought that any planets in orbit would have been destroyed, which may not be the case. PSR 1257+12, now known as Lich, in the constellation of Virgo is one such example of a pulsar with an exoplanet.

There are three possible causes of how a pulsar has orbiting planets.

• Survived Planet - A planet may have survived the explosion if it was sufficiently far away and large enough that only its outer layers were destroyed.
• Zombie Planet - A planet may be reborn from the material expelled from the star consolidating over time.
• Captured Planet - A free-floating planet, a rogue planet may have come too close to the Pulsar and been captured.

Lich was the first star, albeit a dead star, confirmed to have an exoplanet orbiting it. Beta Pictoris in the previous decade was assumed to have an orbiting planet, but it was not confirmed until after Lich's planet was confirmed. The Pulsar was rotating at such a fast speed that scientists could detect the minuscule fluctuation that a planet causes when it orbits around the planet. The planets are bathed in the spinning streams of radiation channelled out from the star, so there is zero chance of life. Trust me; you would not want to live or be anywhere nearby.

It has been theorised though by Cambridge University that life could exist on a Pulsar Planet if the planet was big enough and strong enough to protect the inhabitants. A possible life-supporting Pulsar Planet could be orbiting PSR B1257+12, which has a couple of orbiting Super Earths which have masses 4 and 5 times that of the Earth.

The first extrasolar planet (exoplanet) discovered around a Sun-like star was officially known as 51 Pegasi b and unofficial as Bellerophon after the Greek Mythological character who tamed Pegasus. This winged horse Perseus was used during his mission to save Andromeda from being killed.

There is not even a slight chance that the Lich planet would have life because as the streams cross the planets, they would have destroyed the atmosphere and killed everything. Since Lich's discovery, extrasolar planets have been discovered around so many other stars that we should not feel disheartened that there was no chance of finding a planet that could support alien life there.

Different Pulsar Types

Pulsars can emit different types of radiation, and the common types of Pulsars are:- Swinburne

• Radio Pulsar - These emit radiation in a lighthouse way.
• X-Ray Pulsar - These emit their radiation in X-Ray, and there are two types. These are in binary systems where it is close to a normal star.
  • High Mass X-Ray Binary - assisted by strong stellar winds from a stronger accompanying star
  • Low Mass X-Ray Binary - assisted by a weaker accompanying star
• Optical Pulsar
• Gamma-Ray Pulsar

What is a Magnetar?

Magnetars are Neutron Stars with powerful magnetic fields. They are 100 times stronger than an average neutron star and have a quadrillion times the power of the Earth's Magnetic field. Suppose the Magnetar was as close to the Earth as The Moon, the magnetic strips on your credit cards and render them useless. The Magnetar would lift metal objects off the ground if it were at half the distance. If the Magnetar were 600 miles away, the iron would be stripped from our bodies. There are no magnetars, so do not have nightmares. Ref: Futurism (Link as above).

To give you an idea of how powerful a Magnetar is, the Sun's magnetic field is measured as 5 Gauss. Given that it is the Sun, you would think it is pretty powerful. A magnetar is a thousand times more powerful than a normal neutron star, with a Gauss of a million billion. A known Magnetar is 1E 2259, which is in the constellation of Cassiopeia in the Northern Hemisphere. Ref: N.A.S.A.

The image is courtesy of Nova Celestia which has free use image policy.