Chemical reaction almost as old as the universe was faster than thought

One of the first chemical reactions thought to have occurred in the universe has long posed a conundrum, as it seemed the ancient cosmos was far too cold for it to take place. However, new modeling and experimental evidence now show that the reaction between helium hydride (HeH⁺) and hydrogen was indeed feasible in the primordial universe, a discovery that will help scientists better predict the timing and abundance of the first molecules, stars and galaxies.