A recent study sheds new light on how fluorine, which is found in our bones and teeth as fluoride, is formed in the Universe.
Using the ALMA, A team of astronomers identified this element in a galaxy so far away that its light took almost 12 billion years to reach us.
This is the first time fluorine has been discovered in a star-forming galaxy so far away.
“We all know about fluorine because the toothpaste we use every day contains it in the form of fluoride,” said the study(published in Nature Astronomy ) lead Maximilien Franco from the University of Hertfordshire.
Fluorine, like most elements around us, is created inside stars, but we didn’t know how it was created until today.
“We did not even know which type of stars produced the majority of fluorine in the Universe!”
Franco and his colleagues discovered fluorine (as hydrogen fluoride) in the huge clouds of gas in the distant galaxy NGP–190387, which we see as it was when the Universe was only 1.4 billion years old, or approximately 10% of its present age. Because stars expel the elements formed in their cores as they die, this discovery means that the stars that created fluorine must have lived and died swiftly.
The team says that the most likely fluorine production sites are Wolf–Rayet stars, which are incredibly massive stars that survive for only a few million years, a blink of an eye in the history of the Universe. They are required to explain the levels of hydrogen fluoride discovered by the scientists, according to them. Wolf–Rayet stars had previously been proposed as possible sources of cosmic fluorine, but astronomers did not know how crucial they were in creating this element in the early Universe until now.
“We have shown that Wolf–Rayet stars, which are among the most massive stars known and can explode violently as they reach the end of their lives, help us, in a way, to maintain good dental health!” jokes Franco.
Aside from these stars, additional hypotheses regarding how fluorine is created and evacuated have been proposed in the past. Pulsations of large, evolved stars with masses up to a few times that of our Sun, known as asymptotic giant branch stars, are one example. However, the researchers feel that these scenarios, some of which take billions of years to play out, may not entirely explain the amount of fluorine in NGP–190387.
“For this galaxy, it took just tens or hundreds of millions of years to have fluorine levels comparable to those found in stars in the Milky Way, which is 13.5 billion years old. This was a totally unexpected result,” said Chiaki Kobayashi, a professor at the University of Hertfordshire.
“Our measurement adds a completely new constraint on the origin of fluorine, which has been studied for two decades.”
The discovery of fluorine in NGP–190387 is one of the first beyond the Milky Way and its neighbouring galaxies. This element has previously been discovered in distant quasars, which are brilliant objects fueled by supermassive black holes at the centre of some galaxies. This element, however, had never been discovered in a star-forming galaxy so early in the Universe’s history.
The team’s discovery of fluorine was a coincidental finding made possible by the deployment of space and ground-based observatories. NGP–190387, found with the European Space Agency’s Herschel Space Observatory and afterwards detected with Chile’s ALMA, is unusually brilliant for its distance. The ALMA data confirmed that NGP–190387’s extraordinary luminosity was generated in part by another known large galaxy, lying quite near to the line of sight between NGP–190387 and the Earth. This enormous galaxy enhanced the light noticed by Franco and his colleagues, allowing them to detect the feeble radiation generated by the fluorine in NGP–190387 billions of years ago.
Future investigations of NGP–190387 using the Extremely Large Telescope (ELT) — ESO’s new flagship project, which is currently under construction in Chile and is scheduled to begin operations later this decade — could disclose more secrets about this galaxy.
“ALMA is sensitive to radiation emitted by cold interstellar gas and dust,” said Chentao Yang, an ESO Fellow in Chile.
“With the ELT, we will be able to observe NGP–190387 through the direct light of stars, gaining crucial information on the stellar content of this galaxy.”
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