About J0540+3207
J0540+3207 is an uncommon pulsar. It spins once every 524.271 ms, has a dispersion measure of 61.97 pc cm⁻³ and carries a surface magnetic field around 4.90×10^11 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.