Neutron stars crush more mass than the Sun into a sphere the width of Manhattan, producing matter so dense a single teaspoon would weigh about four billion tonnes on Earth — the mass of a small mountain range in the volume of a sugar cube.
PSR B1919+21, the first neutron star ever detected, was picked up by Jocelyn Bell Burnell in Cambridge in 1967 as a metronome-steady radio pulse arriving every 1.3 seconds from a source no larger tha… [+7326 chars]