Elemental abundances across cosmic time

The chemical composition of a massive galaxy in the early Universe reveals an extremely short period of star formation. This result could challenge our ideas about the evolution of galaxies and of the Universe itself. See Letter p.248 This paper presents the first chemical abundance measurement of a galaxy beyond a redshift of z = 2. It is at z = 2.1, when the Universe was 3 billion years old, and the analysis shows it to be the most magnesium-enhanced massive galaxy found so far, with twice the enhancement found in similar-mass galaxies today. The abundance pattern of the galaxy is consistent with enrichment exclusively by core-collapse supernovae, and a star-formation timescale of 0.1 to 0.5 billion years, making it one of the most vigorous star-forming galaxies in the Universe.