About J1904+0056
J1904+0056 is an uncommon pulsar. It spins once every 438.089 ms, has a dispersion measure of 127 pc cm⁻³ and carries a surface magnetic field around 4.24×10^10 G.
The collapsed core of a star that exploded: about one and a half Suns of matter crushed into a ball the size of a city, held up only by the refusal of neutrons to be squeezed further.