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Neutron Stars

Page history last edited by Jonathan Chung 12 years, 6 months ago



Neutron Stars 

by Jonathan Chung and Jared Kornfield


A neutron star is one of two results of when a massive star ends its life. As we all know, when a massive star dies, the star will create a supernova. From that explosion, the core of the massive star will collapse creating one of two outcomes: a black hole or a neutron star. Neutron stars are composed of neutrons and have about the same mass as protons. Neutron stars are known to have rotation periods of 1.4 ms to 30 seconds.    


How is it created?

The core of a massive star collapses after a supernova.  Even though the neutron star will be about a fraction of what its size was, it keeps the same angular momentum as the original star.      



Do not confuse white dwarfs with neutron stars!

Our Sun does not have enough mass to explode as a supernova, but it will conclude its life as a white dwarf. 

^comparison of the relative sizes of white dwarf, a neutron star, and the earth.^

Structure of the neutron star


theoretical internal neutron star structure



On average models, the matter on the surface of a neutron star is composed of atomic nuclei and electrons. It is the believed that atomic cores at the surface are Ferrum nuclei. The "atmosphere" of the star is roughly one meter thick, below which one encounters a solid "crust". This crust is extremely hard and very smooth because of the extreme gravitational field. Proceeding deeper, one comes to a point called neutron drip where free neutrons leak out of nuclei. In this region, there are nuclei, free electrons, and free neutrons. The nuclei become smaller and smaller until the core is reached, by definition the point where they disappear altogether. The exact nature of the superdense matter in the core is still not well understood. It is believed that Iron exists in the outer core and the inner core consists of Helium and Hydrogen. If the surface temperature exceeds 10Kelvin, the surface should be fluid instead of the solid phase observed in cooler neutron stars.


Rotation of a neutron star


Neutron stars rotate extremely rapidly after their creation due to the conservation of angular momentum. An average neutron star can rotate several hundred times per second. Over time, however, neutron stars slow down because their rotating magnetic fields radiate energy; older neutron stars may take several seconds for each revolution.





^Crab Nebula and the Vela supernova remnants^ 


It is a rare case for a neutron star  to rapidly increase its rotating speed. This sudden increase causes the star to 'spin upwards' therefore creating a 'glitch'. It is believed that these glitches are an effect of starquakes. As the rotation of the star slows down, the shape becomes more spherical. Due to the stiffness of the 'neutron' crust, this happens as discrete events as the crust ruptures, similar to tectonic earthquakes. After the starquake, the star will have a smaller equatorial radius, and since angular momentum is conserved, rotational speed increases.



^Above - an artist's conception of the gamma ray flare expanding from SGR 1806-20.^



Subtypes of Neutron Stars

Radio Quiet Neutron Stars 

Radio Loud Neutron Stars

Quark Star

Preon Star

Q Star




Photo / Illustration Credits:





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