Neutron star

A neutron star is the incredibly dense remnant left behind when a massive star explodes as a supernova, compressing the star's core so tightly that protons and electrons merge into neutrons. These stellar objects are so compact that a teaspoon of neutron star material would weigh as much as a mountain on Earth, yet they can spin hundreds of times per second and emit powerful beams of radiation. Neutron stars represent one of the most extreme examples of matter in the universe and are often detected by astronomers as pulsars when their rotating radiation beams sweep past Earth.