Here is more science to this thread.
As shown previously Fe is the heaviest element that can be produced in the core of stars.
Nuclei heavier than Fe require more energy through supernovae to overcome the Coulomb barrier due to the protons in the nuclei.
Fusion becomes progressively more difficult for heavier nuclei as the Coulomb barrier increases.
One way around this problem is to consider neutron capture (n-capture) as a way of producing heavier nuclei.
Since a neutron has a neutral charge, the Coulomb barrier is overcome.
Nuclei produced in this process have an overabundance of neutrons, are unstable and undergo β-decay to more stable nuclei.
The n-capture process can be broken down into two separate mechanisms an s-process or an r-process.
The s-process or slow process is where the neutron capture time scale τₙ is much longer than the mean time for β-decay τβ.
The r-process or rapid process is where τₙ is much shorter than τβ.
Whereas τβ depends solely on the nuclei, τₙ depends strongly on the environment in particular on the strength of the neutron flux.
Gold is formed via the r-process.
Since the r-process occurs in a shorter time frame an environment of very high neutron flux is required.
The two candidates proposed for such an environment are.
(1) Neutron star mergers.
(2) Type II core type collapse supernovae.
It would appear that option (1) is the main mechanism.
Nature said:
The ejected mass and a merger rate inferred from GW170817 imply that such mergers are a dominant mode of r-process production in the Universe.
Origin of the heavy elements in binary neutron-star mergers from a gravitational-wave event