About J2222-0137
J2222-0137 is a rare pulsar. It spins once every 32.818 ms, has a dispersion measure of 3.28 pc cm⁻³ and carries a surface magnetic field around 4.42×10^9 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.