Neutronium, a hypothetical substance theorized to exist in neutron stars, remains unobserved in space. When a neutron collides with neutronium, it is speculated that it could either become part of the neutronium or potentially cause a release of energy, depending on the neutron's velocity. Neutron capture is a known phenomenon that occurs when a neutron interacts with a nucleus, but its applicability to neutronium is uncertain. The interior of neutron stars is the only known environment where neutrons are stable in large quantities, as they typically decay into protons and electrons. If enough neutrons were bombarded onto a neutron star, it is theorized that this could lead to the star collapsing into a black hole.
