About J1139-6247
J1139-6247 is an uncommon pulsar. It spins once every 120.482 ms and carries a surface magnetic field around 7.07×10^11 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.