Abundance

The chemical composition of these galaxies also suggests that we are getting close to observing objects from the beginning of the cosmic dawn. The first stars should be almost entirely made up of hydrogen and helium; it is only later in their lives that they produce heavier elements. Looking at the earliest stars we have seen,“we can calculate the oxygen, carbon and nitrogen abundance, compared to the sun, and we’re now down to between 1 and 4 per cent at these early times”, says Ellis. “So clearly the universe is heading towards a pristine state in the most distant galaxies that we see.”
–New Scientist