THE NEUTRON STAR, 2023. The Neutron Star coin, the third and final coin in The Uncharted Universe, shows how a massive star, combined with gravitational collapse, becomes one of the densest stellar objects in the universe (2023). In the centre of The Neutron Star coin, a hemisphere curves inwards on one side and outwards on the other. Neutron stars are still something of a mystery, but this little masterpiece makes them a lot more tangible. Among the densest stellar objects in the universe, neutron stars are heavier than the Sun itself. A superb representation of this unique galactic phenomenon, this little beauty weighs considerably less. Featuring a semi-sphere in its centre that curves inwards on one side and outwards on the other, the last coin in The Uncharted Universe series is designed to be a simplified representation of that unique galactic phenomenon – the neutron star. There are thought to be up to one billion neutron stars in the Milky Way. This figure is obtained by estimating the number of stars that have undergone a supernova explosion, a spectacular explosion of a massive star. Combined with gravitational collapse, this creates a compact and super-dense object known as a neutron star. After black holes, neutron stars are the densest stellar objects in the universe.