About J1331-5245
J1331-5245 is an uncommon pulsar. It spins once every 648.117 ms, has a dispersion measure of 148.4 pc cm⁻³ and carries a surface magnetic field around 5.82×10^11 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.