Introductory Astronomy: Neutron Stars

Neutron stars are one of the possible stellar remnants of high mass stars. The mass of a neutron star ranges from 1.4 to 3 solar masses. This is the core mass of the original star, so main sequence stars with much more than 3 solar masses may end up as neutron stars. Neutron stars form when the gravitational pressure is strong enough to force protons and electrons close enough together that they combine into neutrons. At this point, gravitational pressure is balanced by degenerate neutron pressure. Because the force of gravity is so strong, the neutron star is compacted to about 10 to 15 km in size (it could fit inside the DC Beltway). It has a density of about 100 trillion grams per cubic centimeter. As the star collapses, the spin of the star increases (due to conservation of angular momentum, similar to an ice skater spinning faster when he/she pulls his/her arms in) as does the magnetic field. The increased magnetic field causes strong radio emission to occur, and, if this emission crosses our field of view, observers then can observe the neutron star as a Pulsar.