About J1855+0205
J1855+0205 is an uncommon pulsar. It spins once every 246.817 ms, has a dispersion measure of 867.3 pc cm⁻³ and carries a surface magnetic field around 1.28×10^11 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.