About J2238+5903
J2238+5903 is an uncommon pulsar. It spins once every 162.734 ms and carries a surface magnetic field around 4.02×10^12 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.