How Neutron Stars become Pulsars

--------- #1331 - How Neutron Stars become Pulsars?

- Attachment: image of Neutron Star

- Neutron Stars are leftovers after supernova explosions. These smaller stars are the remnant cores of bigger stars. Stars burn their nuclear fusion fuels for millions to billions of years. Big stars burn hotter and have shorter lifetimes, maybe 10 million years.. Smaller stars like our Sun will have a lifetime of some 10 billion years. When the Big Stars go supernovae they leave behind a Neutron Star that can range in mass from 0.7 to 2.7 Solar Mass. However, that mass is concentrated into a rotating sphere that is only 12 miles in diameter.

- When the Big Star starts out it can be 8 to 25 Solar Mass, maybe even as big as 150 Solar Mass. When it runs out of fuel and implodes into a spinning Neutron Star the collapsing outer layers of the star rebound into a titanic explosion hurtling material into outer space. The Neutron Star at the core spins faster in order to maintain the Conservation of Angular Momentum as it collapses to a smaller diameter. This rapid rotation generates a giant magnetic field, like an spinning electric dynamo. The magnetic field generates a current of charged particles that escape out the magnetic poles. Often the beam of particles are offset from the rotational axis causing the beam to rotate like a lighthouse beacon. When the beam flashes across our field of view we call it a “ Pulsar”.

- Only 8 supernovae explosions have been recorded witnessed by the naked eye. One was recorded in August 7, 1181 that lasted for 156 days before becoming too faint for the naked eye. This supernova was designated 3C58. Compared to the Crab Nebula supernova that was witnessed beginning July 4, 1054, 3C58 is 2,000 times weaker in the X-ray spectrum even though the X-ray nebula is several time larger than the Crab.

- It was difficult to find the point source Neutron Star at the center of the nebula. On March 28, 2001 astronomers finally measured the period of this Pulsar at 65.7 milliseconds. This is roughly twice the period of the Crab Pulsar witch is 30 milliseconds. The luminosity was measured at 100,000 Solar Luminosity. The magnetic field was 10 trillion Earth’s magnetic field ,but , about the same as the Crab’s.

- The spin rates of Pulsars slow down as the drag of the strong magnetic fields causes a loss of spin energy. The initial spin rate of the Crab was 19 milliseconds. For 3C58 it was 60 seconds.

- Our Sun’s nuclear fusion creates a surface temperature of 5,800 Kelvin. Temperature is the vibration of atoms and this temperature has a vibration emission wavelength of 500 nanometers, the wavelength of yellow light.

- Neutron Stars have a different source of energy since they no longer have nuclear fuel to generate sunlight. Their spinning magnets generate electric fields that are up to 1,000 trillion volts at the poles. The charged electrons and anti-electrons spiral around these electric field lines. The constant acceleration of charged particles creates a continuous radiation, called synchrotron radiation. In the beginning this energy crates a surface temperature on the Neutron Star of 1,000,000,000 Kelvin. The Neutron Star cools down as it radiates its energy away. After 100 years the surface temperature is still 3,000,000 Kelvin. Escaping neutrinos carry way energy as well as the synchrotron radiation. 3C58 is 820 years old and its surface temperature has cooled to 1,400,000 Kelvin.

- Neutron Stars are so dense because they are collapsed atoms. A hydrogen atom can be compared to a nuclear pea orbited by an electron 200 feet away. Most of the atom is empty space. When the Neutron Star is formed this empty space is collapsed as the electron collides with the proton at the nucleus forming a neutron. When the electrons and protons combine neutrinos are emitted carrying away energy. 80% of the star’s mass is these neutrons with maybe 20% remaining electrons and protons in the outer layers.

- The calculations for 3C58 observed temperatures do not match up with the scenario described above. Something else is going on. Possibly neutrons are breaking down into individual quarks. Possibly other particles are being created and need to be part of the calculations. Possibly particles are up-down-strange quarks creating “ lambdas”. Up-quarks and anti-quarks are creating “pions”. Up-quarks and anti-strange quarks are creating “kaons”. All of these exotic particle creations could increase the stream of neutrinos carrying off more energy and cooling the Neutron Star faster.

- More discoveries are needed to tell us what is going on inside the Neutron Stars. 3C58 has given us more data, but, we need more. An announcement will be made shortly, stay tuned.

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