About J2204+2700
J2204+2700 is a rare pulsar. It spins once every 84.703 ms, has a dispersion measure of 35.07 pc cm⁻³ and carries a surface magnetic field around 3.37×10^9 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.