Ancient stars could create elements with more than 260 protons

The universe’s first stars were terrifying beasts. Composed only of hydrogen and helium, they may be 300 times more massive than the Sun. Inside them, the first heavier elements were formed, which were then thrown out into the universe at the end of their short lives. They were the seeds of all the stars and planets we see today.A new study published in science Showing that these ancient ancestors created more than just natural elements.

With the exception of hydrogen, helium, and small amounts of other light elements, all the atoms we see around us were created through astrophysical processes, such as supernovae, neutron star collisions, and high-energy particle collisions. Together they created the heaviest elements, up to uranium-238, the heaviest naturally occurring element. Uranium is formed in supernovae and neutron star collisions through the so-called r-process, in which neutrons are rapidly captured by atomic nuclei and become heavier elements. The r process is complex, and we still don’t understand how it occurs or what its upper mass limit might be. However, the new study suggests that r-processes in the first generation of stars may have produced much heavier elements with atomic masses greater than 260.

The team looked at 42 stars in the Milky Way, whose elemental compositions were already well understood. Rather than simply looking for the presence of heavier elements, they looked at the relative abundance of elements in all stars. They found that the abundances of some elements, such as silver and rhodium, were inconsistent with the predicted abundances of known r-process nucleosynthesis. The data indicate that these elements are the decay remnants of heavier nuclei exceeding 260 atomic mass units.

In addition to the r-process of rapid neutron capture, there are two other ways to generate heavy nuclei: the p-process, in which neutron-rich nuclei capture protons, and the s-process, in which seed nuclei can capture neutrons. But none of these have the qualities needed to quickly accumulate elements other than uranium. Only in supermassive first-generation stars could r-process nucleosynthesis produce such elements.

Therefore, the research shows that the r-process can produce elements far beyond uranium, and was likely produced in the universe’s first stars. Unless there was an island of stability for some of these superheavy elements, they would have long since decayed into the natural elements we see today. But the fact that they once existed will help scientists better understand the r process and its limitations.