A spoonful that weighs a billion tons

A single spoonful of a neutron star would weigh billions of tons. That is no exaggeration: it is the densest matter we know of, aside from black holes.

A neutron star is what remains when a star much larger than the Sun runs out of fuel and collapses. Its entire mass is squeezed into a sphere barely 20 kilometers across, the size of a city. The atoms are crushed until almost nothing is left but neutrons packed tightly together.

What is more, they spin at dizzying speeds: some turn hundreds of times per second. A thimbleful of that matter, brought to Earth, would weigh more than a mountain.

Source: NASA