About J2124+1407
J2124+1407 is an uncommon pulsar. It spins once every 694.053 ms, has a dispersion measure of 30.25 pc cm⁻³ and carries a surface magnetic field around 7.39×10^11 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.