In a giant cosmic cradle, the Tarantula Nebula, astronomers took a close look at 122 massive stars, each at least 30 times heavier than the Sun. They measured the nitrogen abundance in their atmospheres, and the picture turned out to be unexpected. Almost all stars with masses above one hundred solar masses became "nitrogen champions": their nitrogen levels were 5–10 times higher than standard model predictions.

Nitrogen in such quantities is not just a chemical detail. It is a trace of deep interior processes. In the cores of massive stars, where temperatures and pressures reach unimaginable values, carbon and oxygen are converted into nitrogen. For this nitrogen to reach the surface and become visible, the material must be vigorously mixed. But standard models allow only limited "seepage" of material beyond the convective core. The observations, however, require mixing to be several times stronger.

The scientists tested other explanations. Could it be companion stars that strip off the outer layers? Or particularly strong stellar winds? Or peculiarities of star formation in this nebula? None of these hypotheses could reproduce the observed pattern. The only remaining possibility: mixing is indeed far more efficient. And, apparently, it happens at the very earliest stages of a star's life, or even during its formation.

This puzzle is linked to the distant past of the universe. In the spectra of young galaxies, seen as they were a few hundred million years after the Big Bang, astronomers also find unexpectedly high nitrogen levels. Perhaps the key to this ancient mystery lies in the turbulent interiors of today's stellar giants in the Tarantula Nebula.