A typical neutron star has a mass between about 1.4 and 3.2 solar masses (see Chandrasekhar Limit), with a corresponding radius of about 12 km if the Akmal–Pandharipande–Ravenhall equation of state (APR EOS) is used. In contrast, the Sun's radius is about 60,000 times that. Neutron stars have overall densities predicted by the APR EOS of 3.7×1017 to 5.9×1017 kg/m3 (2.6×1014 to 4.1×1014 times the density of the Sun), which compares with the approximate density of an atomic nucleus of 3×1017 kg/m3. The neutron star's density varies from below 1×109 kg/m3 in the crust, increasing with depth to above 6×1017 or 8×1017 kg/m3 deeper inside (denser than an atomic nucleus). This density is approximately equivalent to the mass of a Boeing 747 compressed to the size of a small grain of sand, or the human population condensed to the size of a sugar cube.
In general, compact stars of less than 1.38 solar masses – the Chandrasekhar limit – are white dwarfs, and above 2 to 3 solar masses (the Tolman–Oppenheimer–Volkoff limit), a quark star might be created; however, this is uncertain. Gravitational collapse will usually occur on any compact star between 10 and 25 solar masses and produce a black hole. Some neutron stars rotate very rapidly and emit beams of electromagnetic radiation as pulsars.
(In the Galactic Chronicle Universe)
NEUTRON STARS are used for Navigation Markers and Union Ships use Known Neutron Stars to deterimine position and course. This is based on the fact that Neutron stars are the remnants of a dying supernova explosion that rotate fast and emit beams perceived as radiation pulses when pointed towards Earth, Blue Moon, Pluribus Etc.. The X rays of these pulsars are used to graph the route of a spacecraft in the intergalactic space. This ground-breaking technology, developed at Max Planck Institute (Germany) allows to monitor the path of the spacecraft anywhere in the solar system or galaxy, as the pulses are produced at regular time periods gap.