4.2. Key observational Requirements
By way of introduction to the data, we list some of the key goals of ongoing
measurements of the primordial abundances.
- 4He : High accuracy, robust measurement in a few places
with the lowest metal abundances.
- 3He : Measurement in gas with much lower metal abundances, or
an understanding of stellar production and destruction and the results
of all stars integrated over the history of the Galaxy
(Galactic chemical evolution).
- D: The discovery of more quasar absorption systems with minimal H
- 7Li : Observations which determine the amount of depletion in
halo stars, or which avoid this problem. Measurement of 6Li ,
Be and B
to help estimate production prior to halo star formation, and
Since we are now obtaining ``precision'' measurements, it now seems best
to make a few measurements with the highest possible accuracy and
controls, in places with the least stellar processing, rather than
multiple measurements of lower accuracy.
We will now discuss observations of each of the nuclei, and especially
D, in more detail.