How ytterbium is formed in the universe – the rare earth metal is formed mainly in supernovae and neutron stars

Rare-earth ytterbium is hermaphrodite: part of this element was formed in the universe when ordinary stars became red giants. But the bulk must have originated in neutron-dense environments such as supernovae or colliding neutron stars, as astronomers have now determined. Thus, the formation of ytterbium is dominated by rapid neutron capture – until now it was not clear which mechanism prevails.

The element ytterbium with atomic number 70 is the second heaviest lanthanide and a rare earth metal. It is used, among other things, in solid-state lasers and plays an important role in it Quantum physics applications and experiences. For example, the first passed time crystals of ytterbium ions and very cold clouds of ytterbium atoms are used to measure time in a very accurate way Quantum atomthe correct

But ytterbium is also special because of its composition: most of the lighter elements are formed by nuclear fusion in sun-like stars or by so-called slow neutron capture (s process) in red giants. On the other hand, heavy elements such as gold, platinum or uranium can only be formed by rapid capture of neutrons. This process r is only for events with high energy neutron density such as a supernova or a supernova neutron star collision possible.

Where was ytterbium formed?

However, ytterbium and some other elements are somewhere in between: a proportion of their atoms can come from red giants, others from supernovae and the like. But what is the dominant ratio? To illustrate this, Martin Montelius of the University of Groningen and his team went looking for clues in the Milky Way. For their study, they analyzed the infrared spectra of 30 massive, massive stars.

The idea behind it: “By examining stars from different ancient regions of the Milky Way, we can determine how quickly the ytterbium content in the galaxy is increasing,” Montelius explains. If ytterbium was formed primarily by rapid capture of neutrons, the element must have been present much earlier than the elements formed after the combustion of low-mass long-stars.

Rapid neutron capture prevails

In fact, the evaluation showed the following: Compared with the lighter rare-earth metal cerium, which is dominated by the slow s process, the high-energy r process appears to predominate in ytterbium. So the element must have formed mostly in supernovae for massive stars. “However, the s process also plays a certain role in ytterbium, as predicted by theoretical models,” the researchers say.

The method used by astronomers could also be suitable for investigating the origin of other elements with unclear formation paths. Conversely, the discovery of ytterbium strain in stars can now help reconstruct the history of stars and galactic regions, the team explains. (Astronomy and Astrophysics, submitted; R-Access: 2202.00691)

Source: Lund University

March 8, 2022

– Nadia Podebrigar