In the known universe, there is nothing quite like a neutron star. Born from supernovas, these objects contain a star-size mass in a city-size space. This unique trait has led scientists to believe that some extreme physics might take place in their innards — perhaps even
the dissolution of neutrons themselves into a softer goo known as quark matter.
Yet we cannot peer inside neutron stars, so we must rely on the characteristics we can measure, namely their mass and size. Quark matter should be more compressed by the star’s gravity than intact neutrons, so if neutron stars are full of nuclear goo, they should not only be small, but grow smaller as their masses increase.
