Neutron Star

A neutron star is the dead remnant of a massive star. A massive star ends its life as a supernova, a catastrophic explosion that flings the star's outer layers into space, leaving only the core behind. If the mass of the core is between 1.4 and 2.5 times the mass of the Sun, it will become a neutron star, a solid mass of neutrons a hundred trillion times more dense than water. Neutron stars are tiny, about 6.2 mi (10 km) across, and they rotate very rapidly and have tremendously strong magnetic fields. Because they are massive and small, they also have intense gravitational fields. They are most easily observed in the radio and x ray portions of the spectrum, so they were not discovered until the late 1960s, when radio and x ray telescopes capable of detecting them began to become available.