About J1623-2631
J1623-2631 is a rare pulsar. It spins once every 11.076 ms, has a dispersion measure of 62.86 pc cm⁻³ and carries a surface magnetic field around 2.76×10^9 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.