About J2222+2923
J2222+2923 is an uncommon pulsar. It spins once every 281.399 ms, has a dispersion measure of 49.41 pc cm⁻³ and carries a surface magnetic field around 4.22×10^10 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.