Formation of Neutron stars and Pulsars

Neutron Star Formation

When a massive star reaches the end of its life, it goes out with a bang, in the form of a supernova.[1] The extravagant stellar explosion causes the remnant core to collapse into itself, and the intense gravitational field shrinks the core into a compact sphere, roughly 10-20 km in diameter.[1] This means that it would take roughly ten million average sized neutron stars to fill up a space the size of our moon! The gravity on a neutron star is so strong, that it actually compresses its comprising atoms enough to pull the electrons into the protons, creating a sea of neutrons, and hence the name “Neutron Star”.[1][2]

Pulsar Formation

When a neutron star is formed, a lot of the giant core of the preexisting star is compressed back into a hot, dense ball. Conservation of angular momentum plays a key role in the formation of pulsars, and is crucial to understand to understand pulsars.[2] Angular momentum is the momentum of rotation. Consider a figure skater spinning on the ice with her arms out. If the skater is spinning continuously without any external forces disturbing her, then the angular momentum can be said to be constant. Now, if she pulls her arms into her body, her rotation speed will greatly increase, since her pulled her body in closer to the axis of rotation, and because angular momentum has not increased or decreased in the process. Similarly, since angular momentum of the preexisting massive star is conserved, and the radius of the star is drastically reduced after neutron star formation, the neutron star generally acquires a very high rotation speed, sometimes up to hundreds of times per second![2]



[1] Robbins, Stuart, McDonald, David. “Neutron Stars and Pulsars.” Welcome to Journey Through the Galaxy. N. Case Western Reserve University, 1997. Web. 15 Mar. 2013.
[2]Mattson, Barbara. “Neutron Stars and Pulsars.” Imagine the Universe! N.p, 1997. Web. 15 Mar. 2013.