About J1931+1952
J1931+1952 is an uncommon pulsar. It spins once every 501.123 ms, has a dispersion measure of 441 pc cm⁻³ and carries a surface magnetic field around 2.27×10^11 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.