About J1900+0634
J1900+0634 is an uncommon pulsar. It spins once every 389.869 ms, has a dispersion measure of 323.4 pc cm⁻³ and carries a surface magnetic field around 1.43×10^12 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.