About J1957+2831
J1957+2831 is an uncommon pulsar. It spins once every 307.683 ms, has a dispersion measure of 138.99 pc cm⁻³ and carries a surface magnetic field around 9.90×10^11 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.