The initial stars of the cosmos were colossal entities, consisting solely of hydrogen and helium, boasting masses potentially 300 times greater than the sun. Within these celestial giants, the inaugural heavier elements took shape, subsequently being expelled into the cosmic expanse as these stars met their brief demise. These primordial entities laid the foundation for the multitude of stars and planets that grace our skies today. A recent study, featured in the journal Science, proposes that these ancient progenitors not only birthed natural elements but also contributed to the creation of elements beyond our previous understanding.
With the exception of hydrogen, helium, and a handful of other light elements, all the atoms constituting the world around us emerged from astrophysical phenomena. Processes like supernovae, neutron star collisions, and high-energy particle collisions collectively forged heavier elements, culminating in Uranium-238, the heaviest naturally occurring element. Uranium forms through the r-process, a mechanism where neutrons swiftly amalgamate with atomic nuclei, transforming into a weightier element. Despite its significance, the r-process remains intricate, harboring much that eludes our comprehension, including the upper mass limit of its outcomes. The recent study, however, postulates that the r-process in the inaugural stars might have given rise to elements surpassing atomic masses of 260.
The research scrutinized 42 stars within the Milky Way, each possessing a well-defined elemental composition. Rather than merely identifying the presence of heavier elements, the scientists delved into the relative abundances of elements across these stars. Intriguingly, they observed disparities in the abundance of certain elements, such as silver and rhodium, when compared to anticipated values from established r-process nucleosynthesis. This incongruity hints at these elements being remnants from the decay of much weightier nuclei surpassing 260 atomic mass units.
While other mechanisms, like the p-process and s-process, also contribute to the creation of heavy atomic nuclei, neither can engender the rapid mass accumulation requisite for elements surpassing uranium. The study posits that it is solely within the hypermassive first-generation stars that r-process nucleosynthesis could have produced these exceedingly heavy elements.
Consequently, the findings propose that the r-process might be responsible for generating elements extending beyond uranium, particularly within the nascent stars of the universe. Unless there exists an enclave of stability for some of these ultra-heavy elements, they likely disintegrated eons ago, leaving behind the natural elements we observe today. Nonetheless, their existence in the past contributes invaluable insights to our comprehension of the r-process and its limitations.
Source: Universe Today