Ask Ethan: How are the heaviest elements of all made? | by Ethan Siegel | Starts With A Bang! | Jan, 2025

Matter is made up largely of atoms, where atomic nuclei can contain up to 100 protons or more. But how were the heaviest elements made?

Across the Universe, in all directions, there’s practically nowhere we can look that isn’t filled with some sort of matter: stars, galaxies, dust, gas clouds, and plasma chief among them, with small bodies scattered throughout each individual stellar system. When we examine this matter in detail, we find that it isn’t just made of the most common elements — hydrogen, helium, oxygen, carbon, and more — but that the full suite of elements found in the periodic table are found in various amounts all across the Universe. Here in our Solar System, we’ve been able to identify the abundance of these elements most precisely, but we also find them elsewhere: in and around newborn stars, in the interstellar medium, in supernova and kilonova remnants, in planetary nebulae, and much, much more.

But how, where, and when are these elements made? And, in particular, while the lighter elements are relatively easy to make, there are only two sources of production for the heaviest of all; why is that? That’s what Vince Tseng wants to know, asking:

“My question is on how the heaviest elements are…