Free Astronomy Magazine January-February 2022

25 JANUARY-FEBRUARY 2022 ASTRO PUBLISHING “We all know about fluorine be- cause the toothpaste we use every day contains it in the form of fluo- ride,” says Maximilien Franco from the University of Hertfordshire in the UK, who led the new study, published in Nature Astronomy . Like most elements around us, fluo- rine is created inside stars but, until now, we did not know exactly how this element was produced. “We did not even know which type of stars produced the majority of fluorine in the Universe!” Franco and his collaborators spot- ted fluorine (in the form of hydro- gen fluoride) in the large clouds of gas of the distant galaxy NGP– 190387, which we see as it was when the Universe was only 1.4 bil- lion years old, about 10% of its cur- rent age. Since stars expel the elements they form in their cores as they reach the end of their lives, this detection implies that the stars that created fluorine must have lived and died quickly. The team believes that Wolf–Rayet stars, very massive stars that live only a few million years, a blink of the eye in the Universe’s history, are the most likely production sites of fluorine. They are needed to explain the amounts of hydrogen fluoride the team spotted, they say. Wolf– Rayet stars had been suggested as possible sources of cosmic fluorine before, but astronomers did not know until now how important they were in producing this element in the early Universe. “We have shown that Wolf–Rayet stars, which are among the most massive stars known and can ex- plode violently as they reach the T his artist’s impression shows NGP–190387, a star-forming, dusty galaxy that is so far away its light has taken over 12 billion years to reach us. [ESO/M. Kornmesser]