My astronomy book reads, “Heavy-element fusion in massive stars ends with iron.” How are elements heavier than iron in the periodic table created?

In certain environments (such as a supernova), an iron nucleus can capture neutrons. Eventually, one of those neutrons will convert into a proton, an electron, and an antineutrino. This process, called “neutron capture,” then changes the iron nucleus (26 protons) to a cobalt nucleus (27 protons). These events repeat to create heavier elements.