Scientists have discovered how fluorine – which we mainly know in the form of fluoride – is formed.

You’ve probably heard of fluorine, or fluoride. Fluoride is a trace element that we find in our teeth and bones, for example. “We are all familiar with fluorine,” says researcher Maximilien Franco. “In the form of fluoride, for example, it is in your toothpaste that we use every day.” Like most elements around us, fluorine is produced inside stars. But how exactly that happens has been a mystery until recently. “‘We didn’t even know what type of stars produced most of the cosmic fluorine!” exclaims Franco.

Formation

But in a new study, researchers are changing that. Scientists have discovered how fluorine is formed. Using the Atacama Large Millimeter/submillimeter Array (ALMA), a research team has discovered this element in the large gas clouds of a distant galaxy. In fact, this galaxy is so far away that it took light more than twelve billion years to reach us.

galaxy

The galaxy in question is known as NGP-190387. And with the help of powerful telescopes, we can see this distant galaxy as it looked when the Universe was only 1.4 billion years old (that’s only 10 percent of its current age). The researchers found that NGP-190387 harbors fluorine (in the form of hydrogen fluoride). An interesting find. Since stars emit the elements they form in their cores when they reach the end of their lives, this detection implies that the stars that made the fluorine probably only lived a short time.

Artistic impression of NGP-190387; a star-forming, dusty galaxy so distant that its light took more than twelve billion years to reach us. Image: ESO/M. kornmesser

What type of stars in this galaxy produce fluorine? The team suspects that so-called Wolf-Rayet stars are the main producers. Wolf-Rayet stars are massive stars with masses over 20 solar masses that live for only a few million years – the twinkling of an eye in cosmic terms. Although Wolf-Rayet stars have been suggested as possible sources of cosmic fluorine, until now astronomers were unaware of their importance in producing this element in the early Universe. “We’ve shown that Wolf-Rayet stars, which are some of the most massive stars we know and can explode violently at the end of their lives, in a way help us maintain healthy teeth,” Franco jokes.

Scoop
The discovery of fluorine in NGP-190387 is quite special. This is the first time that fluorine has been observed in such a distant star-forming galaxy. In addition, it is one of the first observations of fluorine outside the Milky Way galaxy and neighboring galaxies. However, astronomers have previously spotted this element in distant quasars — bright objects powered by supermassive black holes at the centers of some galaxies. But never before had this element been observed in a galaxy so early in the history of the universe.

The new discovery sheds light on how fluorine is produced in the universe. Because we now know that healthy teeth are actually made possible in a certain sense by super-heavy Wolf-Rayet stars. Think about that when you brush your teeth again tonight.