About J1231-4609
J1231-4609 is an uncommon pulsar. It spins once every 877.239 ms, has a dispersion measure of 67.4 pc cm⁻³ and carries a surface magnetic field around 1.85×10^11 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.