When Was the First Caesium-133 Atom Formed in the Universe?

[Verdict]

Dear Physicsforum,
I have a rather simple question, which can probably also be solved with a rather simple answer. I am writing a paper on the history of the perception of time, on the scale of the big bang up until now. In this I use that nowadays the definition of 1 second is based on Caesium-133 atoms. I was wondering if you could tell me when (approximately) the first Caesium-133 were formed in our universe, as this is, in a very abstract way, the origin of the modern second. Information about the process itself would be welcome. As far as I can tell, it is probably like all the other heavy elements, as in that it was formed in supernovae, however I remain uncertain.
What I found on my own was that several of the Caesium isotopes are synthesized from lighter elements by the slow neutron capture process (S-process) inside old stars, as well as inside supernova explosions (R-process), however it doesn't specify if the 133 variant is among them.
Would it be wrong to assume that the first supernovae occurred around the time the first stars formed, ~400 million years after the big bang? And would, if I can assume that, it be fair to say that the first Caesium-133 might also have been formed at that point?

I understand that this doesn't fit the standard format of the homework questions, and I apologize if this is not what this forum is designated for.

Thanks in advance

 

[member 553083]

!The formation of Caesium-133 is a complex process, with different isotopes being formed in different stages. While most of the heavier elements (such as Caesium-133) are formed in supernovae, some of its isotopes can also be formed by the slow neutron capture process (S-process) inside old stars. The exact timeline of its formation is difficult to determine, but it is estimated that the first stars were formed around 400 million years after the Big Bang, and that supernovas began forming shortly thereafter. Therefore, it is reasonable to assume that the first Caesium-133 atoms were likely formed in the first few supernovas that occurred in our universe.