TheSkySearchers

helicon wrote: ↑Tue Sep 15, 2020 9:02 pm Very interesting and I'm sure the follow up research to the fact that they are primarily pointing out deficiencies in accepted theory will be instructive. The question of the missing gold is not solved in the article.

seigell wrote: ↑Tue Sep 15, 2020 10:19 pm @nFA: Interesting article, but like many which are attempting to present salient elements of a technical document to a lay audience, it seemed that the sensational points (too much gold - too few neutron star mergers) were focused on at the expense of even a simple background primer.

Case in point: The article makes an effort to reference the types of star deaths and the elements that are likely produced, but made no real effort to describe how or where the relative abundances of elements were derived. We know that one method is spectroscopic analysis of brighter (bright-enough) stars. Where is the limit to which spectroscopy is capable of element analysis??

I know that it can determine compounds in the atmospheres of nearby planets and stars. And can determine metalicity of brighter stars in distant globular clusters; and even redshift in very distant galaxies. But can it determine the quantities of heavier elements than hydrogen and helium in distant stars - say globular clusters or satellite dwarf galaxies??

Or further distances??

Can one even determine the stellar composition to any depth below the chromosphere??

So, are elemental abundances solely extrapolated from spectrographic sampling of nearby stars?? Could this census be skewed by compositional oddities of our stellar neighborhood?? Could we simply be Gold-rich and Silver-poor within our neighborhood??

To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C (A = 12) to U (A = 238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M > 30M⊙ can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M ~ 20–50M⊙. The contribution to GCE from super-asymptotic giant branch (AGB) stars (with M ~ 8–10M⊙ at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements (Sr, Y, Zr) are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ~3% of 25–50M⊙ HNe are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with Galactic archeology surveys.