James Lattimer has made a number of fundamental contributions to the field of nuclear astrophysics with a particular focus on neutron stars, which are ultra-dense objects formed in supernova explosions. In 1974, he proposed that the origin of many heavy elements stems from neutron star mergers, which should soon be observed in gravitational radiation. In 1986, he computed the neutrino signal from supernova that matched observations of a nearby supernova in 1987. In 2011, his team discovered superfluidity in the core of a neutron star for the first time.