From the December 2010 issue

How the Big Bang forged the first elements

The paltry amount of lithium in ancient stars raises questions about exactly how nucleosynthesis played out in the early universe. But cosmologists have a pretty good handle on how nuclear reactions created hydrogen and helium.
By | Published: December 27, 2010 | Last updated on May 18, 2023
Nearby globular cluster NGC 6397 contains hundreds of thousands of ancient metal-poor stars (those that have few elements heavier than helium). Observations of a few hundred of these stars show that those burning hydrogen into helium all have about the same abundance of lithium.

Hydrogen and helium — the two lightest elements — make up some 98 percent of the universe’s mass. It may seem surprising, then, to learn that scientists figured out where the heavier elements came from before they understood the big two.