Scientists have successfully recreated the earliest post-Big Bang chemical reactions under primordial universe-like conditions for the first time. The breakthrough, published in *Astronomy & Astrophysics* by researchers at Germany’s Max Planck Institute for Nuclear Physics, could help reconstruct the cascade of events leading to the first stars.
The experiment employed the institute’s unique Cryogenic Storage Ring in Heidelberg—a world-exclusive instrument for studying molecular and atomic reactions in deep-space conditions. This ring-shaped device stores high-energy particle beams at temperatures just a few degrees above absolute zero.
Using this infrastructure, the team replicated reactions triggered by the universe’s first molecule, helium hydride ion (HeH⁺), formed when a neutral helium atom fused with an ionized hydrogen atom. These reactions paved the way for molecular hydrogen (H₂)—the universe’s most abundant molecule and the building block of stars.
Specifically, the study examined interactions between helium hydride ions and deuterium (a hydrogen isotope with an extra neutron). Unexpectedly, results revealed the reaction rate remains unaffected by temperature drops, suggesting it played a far greater role in early-universe chemistry during the cooling phase than previously thought.