About J1840+0214
J1840+0214 is an uncommon pulsar. It spins once every 797.478 ms, has a dispersion measure of 182.4 pc cm⁻³ and carries a surface magnetic field around 2.60×10^12 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.