Abstract
After a supernova explosion, if the remaining core does not exceed 3 solar masses, it can remain in equilibrium as a neutron star. It is the Pauli pressure of the degenerated neutrons that compensates for gravity. The explosion of the Crab supernova in 1054 gave rise to such a star, which today rotates on itself with a period of 33 milliseconds. Its density is of the order of a billion tonnes per cubic centimetre, and its core is said to be a purée of quarks.
