About J1919+0021
J1919+0021 is an uncommon pulsar. It spins once every 1,272.26 ms, has a dispersion measure of 90.31 pc cm⁻³ and carries a surface magnetic field around 3.16×10^12 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.