The interpretation of elements found in a star's atmosphere is very important because the elements are assumed to be part of the star, not acquired from something external.
Safire observed elements on the globe that were not from the globe or the test's environment.
In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium.
Astronomers believe the fusion core could create heavier elements but there is no mechanism to get them out to the atmosphere. Astronomers believe the heavier elements were within the cloud that formed the star. These heavier elements got into interstellar space from supernova cataclysmic explosions.
The interpretation is more heavier elements means the star was formed in an environment affected by more supernovae over many years. The metallicity is assumed to be directly related to the star's age.
This method was recently found to be invalid.
On August 8, I posted about a star being dated as older than the universe. Clearly that combination is impossible. The assumptions are wrong.
On October 4, I posted about globular cluster stars with a reference to a study of GC stars motion and metallicity. Astronomers use the mix of metallicity to estimate the age of the entire GC.
In light of the Safire observation a GC is a more complex environment for a star. Our Sun is relatively distant from other stars but in a GC the distances are shorter.
One could suggest the stars in the GC could get changes in their atmosphere from either a process like observed by Safire or from an interstellar medium in the GC which is more polluted than expected.
This problem is like radioactive decay dating which is corrupted by the introduction of the decay elements to the atom being dated.
Safire suggests changes occur within the atmosphere of a star. Metallicity usage assumes a) there are none, and b) the interstellar medium is irrelevant after the star forms.
Using metallicity for determining an age is not as reliable as claimed, wherever the star is located.
I found a paper titled 'Measuring age, metallicity and abundance ratios from absorption-line indices'
The big problem is finding a star with its age known with certainty to test the algorithm.