“It takes us one step further.”
A group of researchers have succeeded in finding for the first time what they term “fingerprints” left by the explosion of the first stars of the universein the form of three gas clouds whose chemical composition coincides with that to be expected from those original stellar phenomena.
A group of scientists from France, Italy, the United States, Canada and Chile used the VLT (Very Large Telescope) telescope at the Atacama observatory (Chile) to detect this trace that, they say, “takes us one step further to understand the nature of the first stars that formed after the Big Bang,” according to a statement from the European Southern Observatory (ESO).
“For the first time we have been able to identify the chemical trace of the explosions of the first stars in very distant gas clouds,” according to Andrea Saccardi, a PhD student at the Observatoire de Paris – PSL, who led this study for his thesis at the University of Florence (central Italy).
They appeared 13.5 billion years ago.
Researchers believe that the first stars to form in the universe were very different from those we know today. When they appeared 13.5 billion years ago had only hydrogen and helium, the simplest chemical elements in nature.
Those stars, which are thought to have been tens or hundreds of times more massive than the Sundied quickly in powerful explosions known as supernovae and enriched the surrounding gas with heavier elements for the first time.
Later generations of stars were born from that enriched gas and expelled heavier elements in turn when they died. But since the first stars disappeared a long time ago the challenge is to find out. how to know more about them.
According to Stefania Salvadori, assistant professor at the University of Florence and co-author of the study, published Wednesday in the Astrophysical Journal, “the primordial stars can be studied indirectly by detecting the chemical elements they dispersed in their environment after their death.”
The team of researchers found three very distant clouds, perceived when the universe was between the 10 to 15% of its age present, with chemical fingerprints matching those expected from the explosions of the first stars.
Depending on their mass and the energy in their explosions, those early supernovae released different elements chemicals, such as carbon, oxygen, and magnesium, present in the outer layers of the stars. But some of the explosions were not energetic enough to release heavier elements, such as iron, which is only found in the core of the stars.
The researchers analyzed distant clouds with little iron but rich in other elements and found that three of them, very distant ones, had very little iron but a lot of carbon and other elements, the “fingerprints” of the explosions of primordial stars.
That chemical composition has also been observed in many old stars in our own galaxy, which researchers believe contains second-generation stars that formed directly from the “ashes” of the former.
This study thus adds a missing piece to the puzzle and. “opens up new avenues to the indirect study of the nature of the first stars, thus fully complementing the studies of the stars in our galaxy,” according to Salvadori.
Discovery with light beams
To get to these clouds, the researchers used beams of light known as quasarswhich are very bright sources powered by supermassive black holes at the center of distant galaxies. As it travels through the universe, the light from a quasar passes through gas clouds and the different chemical elements in the clouds leave an imprint on it.
The team observed and analyzed data from several quasars detected by the ESO VLT telescope’s X-shooter instrument, which separates light into extremely broad wavelengths, or colors, making it a unique tool for identifying many different chemical elements in gas clouds.
According to Valentina D’Odorico, a researcher at Italy’s National Institute of Astrophysics and co-author of the study, this. opens the way to the next generation of telescopes and instruments, such as ESO’s upcoming ELT (Extremely Large Telescope) and its high-resolution spectrograph ANDES (ArmazoNes high Dispersion Echelle Spectrograph).
D’Odorico advances that with both it will be possible to. “to study many of these rare clouds of gas in greater detail and we will be able to finally discover the mysterious nature of the first stars.”