A galaxy 12 billion light-years away from Earth has detected fluorine, an element found within our teeth and bones as fluoride.
This is the most distant detection of the chemical so far, according to astronomers from the University of Hertfordshire, who used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to make the discovery.
We can see the fluorine from this great distance. It was only 1.4 million years after the Big Bang. That’s about 10% of the age of the universe.
Maximilien Franco, a study author, said that fluorine, like most elements around us is made in stars, but that we didn’t know how it was created.
Franco and colleagues found hydrogen fluoride in the large clouds of gas of the distant galaxy NGP–190387, the light of which was produced 12 billion years ago, and is only just reaching us.
Stars release heavier elements towards the end, and this fluorine was discovered when the universe was only 1.4 billion years old. This suggests that the stars that created it must have lived and passed away very quickly, the team stated.
They believe that Wolf–Rayet stars, very massive stars that live only a few million years, are the most likely production sites of fluorine.
Franco and colleagues found hydrogen fluoride in the large clouds of gas of the distant galaxy NGP–190387 (artist impression pictured), the light of which was produced 12 billion years ago, and is only just reaching us
Astronomers have not been able to determine how fluorine was created, or which stars were responsible, particularly in the early universe.
Franco said, “We all know fluorine because toothpaste we use every single day contains it in the form fluoride.”
“We didn’t even know which stars produced the most fluorine throughout the universe!”
ALMA was used by the researchers to examine an ancient cloud of gas for telltale signs of the chemical.
The light they saw was visible from the universe’s 1.4 billion year old age, or about 10% of its current age.
Chemicals are made in the hearts of dying stars. They fuse heavier elements as they run out hydrogen and helium, before eventually shedding their matter and creating a cloud of gas.
Fluorine was discovered 1.4 billion years after the Big Bang. This implies that stars responsible for creating fluorine must have lived and died quickly.
Wolf-Rayet stars are one of the few that can explain these rapid expulsion, as they only live a few million years, a blink of the eye in the universe’s history.
The team stated that their models require this rapid life cycle in order to explain the high levels of hydrogen fluoride they observed.
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 explode violently as they reach the end of their lives, help us, in a way, to maintain good dental health!’ Franco jokes.
The origin of fluorine was previously explained by pulsations from giant, evolved stars with masses several times greater than the sun.
These are known as asymptotic giant branch stars, but the team believes these scenarios, some of which take billions of years to occur, might not fully explain the amount of fluorine in NGP–190387.
They believe that Wolf–Rayet stars (artist impression), very massive stars that live only a few million years, are the most likely production sites of fluorine.
“For this galaxy, it only took tens of hundreds of millions of year to attain fluorine levels comparable with those found in stars in our Milky Way, which is 13.5billion years old. This was an unexpected result,” Chiaki Kobayashi co-author.
“Our measurement adds a completely different constraint on fluorine’s origin, which has been studied over the past two decades.”
This is also the first time that fluorine has ever been seen beyond the Milky Way, and other galaxies.
It has been observed in distant quasars and bright objects powered by supermassive dark holes at the centres of some galaxies. But it was never seen in a star-forming Galaxy so early in the universe.
It was a chance discovery by the team, who stated that it was possible only because of a combination space-based and ground-based observatories.
NGP–190387 was first discovered by the European Space Agency’s Herschel Space Observatory and later observed with the Chile-based ALMA.
According to the team it is exceptionally bright for its distance.
This brightness was caused by another massive galaxy that was situated between it and the Earth at the line of sight.
This closer massive galaxy amplified the light observed by Franco and his collaborators, enabling them to spot the faint radiation emitted billions of years ago by the fluorine in NGP–190387.
NGP–190387 was first discovered by the European Space Agency’s Herschel Space Observatory and later observed with the Chile-based ALMA. This is a wide field view of the space where it was discovered. Although it isn’t visible here it is close to the centre of the image.
Researchers plan to make use of the Extremely Large Telescope, which is also operated by the European Southern Observatory, to observe distant galaxies in much greater detail.
Chentao Yang is an ESO Fellow in Chile. Chentao Yang says that ALMA is sensitive radiation emitted from cold interstellar dust and gas.
‘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.’
The journal Nature Astronomy published the findings.
What is ALMA?
Deep in Chile’s desert, the Atacama Large Millimetre Array or ALMA is found in one of the driest areas on Earth.
The construction of the aircraft was completed at an altitude of 16,400ft. This is approximately half the cruising height for a jumbo jet, and nearly four times that of Ben Nevis.
It was switched on March 2013 and is the world’s strongest ground-based telescope.
It is also the highest on the planet and, at almost £1 billion ($1.2 billion), one of the most expensive of its kind.
The Atacama Large Millimetre Array or ALMA is located deep in the Chilean desert. It is the most powerful ground-based telescope in the world, having been switched on in March 2013.