We only know the masses of a few neutron stars, most between the mass of the Sun, and two times the mass of the Sun. Can heavier ones exist in Nature, or do they all turn into black holes? Explore the stellar graveyard on your own with this interactive tool at CIERA. ***https://ciera.northwestern.edu/gallery/masses-in-the-stellar-graveyard/*** [Image: Frank Elavsky/Northwestern University]