Neutron star

A neutron star is the collapsed core of a massive supergiant star. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density, composed mostly of tightly-packed neutrons (neutronium). Some may continue collapsing to form a black hole.

Most neutron stars rotate rapidly, with periods ranging from a few seconds down to milliseconds. The fastest rotate over 700 times a second, and combined with such dense gravities should emit gravitational waves. Highly energetic neutron stars emit rapid, regular pulses of electromagnetic radiation, and are known as pulsars; the most extreme examples of these objects are known as magnetars. A neutron star merging with another creates immense magnetic fields and short gamma-ray bursts.

Neutron stars hold exotic forms of matter:

 * Neutronium which is equivalent to a chemical element with atomic number 0, has zero protons or electrons, is extremely radioactive, and decays quickly into hydrogen. Neutronium matter can degenerate into degenerate matter or strange matter (during core collapse) which is much denser.
 * Degenerate matter is neutron degeneracy with a density magnitude of 1017 kg/m3, or up 1018 kg/m3 in the core.
 * Strange matter is quark matter containing strange quarks in the core of many neutron stars, varying in size from femtometers (strangelets) to kilometers. Strange matter has a density magnitude of 1017 kg/m3, whereas ordinary atoms are in the picoscale range (1012 kg/m3). A neutron star with a quark matter core is a hybrid star or strange star.
 * Magmatter is denser, at around 1018 kg/m3, formed in the core during the stages of collapse into a black hole, and monopoles are released as radiation.