About J0312-0921
J0312-0921 is an epic pulsar. It spins once every 3.704 ms, has a dispersion measure of 20.5 pc cm⁻³ and carries a surface magnetic field around 273,520,050 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.