What was the source of the lightest nuclei, like deuterium, in the universe? Where were the rest of the elements in the periodic table through uranium produced?

Within the first few minutes after the Big Bang, when the universe was incredibly hot and dense, the process of Big Bang nucleosynthesis took place. During this process, protons and neutrons combined to form the lightest nuclei, including deuterium (\(^2_1\)H), helium-4 (\(^4_2\)He), and small amounts of lithium-7 (\(^7_3\)Li) and helium-3 (\(^3_2\)He). Deuterium was formed when a proton captured a neutron, resulting in a deuterium nucleus.

The elements in the periodic table heavier than helium, up to uranium, were primarily formed through two processes: stellar nucleosynthesis and supernovae explosions. 1. Stellar nucleosynthesis: Inside the cores of stars, nuclear fusion processes occur that create heavier elements from lighter ones. For example, hydrogen fusion (the proton-proton chain or the CNO cycle) forms helium, while helium fusion (the triple-alpha process) creates carbon and oxygen. Additional fusion processes in more massive stars, such as the CNO cycle and the s-process, create elements up to iron (\(^{56}_{26}\)Fe). 2. Supernovae explosions: When a massive star exhausts its nuclear fuel and collapses, a supernova explosion occurs. In this extreme environment, rapid neutron-capture processes, such as the r-process and the rp-process, create heavy elements beyond iron, including elements in the periodic table up to uranium (\(^{238}_{92}\)U). Supernovae explosions also serve as the mechanism for distributing the newly formed elements into the interstellar medium, contributing to the enrichment of succeeding generations of stars and their planets.