Astronomers may have discovered the ancient chemical remnants of the first stars that illuminated the universe. Scientists’ innovative analysis of distant quasars observed by the 8.1-meter Gemini North Telescope in Hawaii, operated by the National Science Foundation’s NOIRLab, has uncovered an unusual ratio of elements they believe could only come from all Earth resulting fragments. – The explosion of a first-generation star of 300 solar masses.
The earliest stars may have formed when the universe was only 100 million years old, less than 1% of its current age. These first stars — known as the third population — were so massive that when they ended their lives in supernovae, they tore themselves apart, seeding interstellar space with a unique mix of heavy elements. However, despite decades of painstaking searches by astronomers, there has been no direct evidence of these primordial stars until now.
By analyzing one of the most distant known quasars  Using the Gemini North telescope, one of two identical telescopes at the International Gemini Observatory operated by NSF’s NOIRLab, astronomers now think they have identified the remnants of the first generation of stellar explosions. Using an innovative method to infer the chemical elements contained in the clouds around quasars, they noticed a very unusual composition — a material that contains a ratio of iron compared to the proportions of these elements found in our sun More than 10 times more magnesium.
Scientists believe the most likely explanation for the striking feature is that the material was left behind by a first-generation star that exploded as a pair of unstable supernovae. These very powerful supernova explosions have never been witnessed, but are theoretically the end of life for giant stars 150 to 250 times the mass of the Sun.
Pair-instability supernova explosions occur when photons at the center of a star spontaneously become electrons and positrons—the positively charged antimatter counterparts of electrons. This conversion reduces the radiation pressure inside the star, allowing gravity to overcome it and cause the collapse and subsequent explosion.
Unlike other supernovae, these dramatic events don’t leave behind stellar remnants, such as neutron stars or black holes, but instead eject all of their material into their surroundings. There are only two ways to find evidence of them. The first is to catch an unstable pairing supernova when it happens, which is extremely unlikely to happen. Another approach is to identify their chemical signatures from the materials they eject into interstellar space.
In their study, the astronomers looked at the results of previous observations made by the 8.1-meter Gemini North Telescope using the Gemini Near Infrared Spectrometer (GNIRS). Spectrometers separate the light emitted by a celestial body into its constituent wavelengths, which carry information about which elements the celestial body contains. Gemini is one of the few telescopes with the right equipment for such observations.
Inferring the amount of each element present is tricky, however, because the brightness of a line in the spectrum depends on many other factors besides element abundance.
The two co-authors of the analysis, Yuzuru Yoshii and Hiroaki Sameshima of the University of Tokyo, addressed this question by developing a method that uses wavelength intensities in the quasar’s spectrum to estimate the abundance of elements present there. It was by using this method to analyze the spectra of quasars that they and their colleagues found a significantly low ratio of magnesium to iron.
“It seems obvious to me that a supernova candidate would be a pair of unstable supernovas of a third group of stars, where the entire star explodes without leaving any remnants,“Yoshii said.”I was pleased and a little surprised to find that a double unstable supernova of a star with a mass about 300 times the mass of the Sun provides a ratio of magnesium to iron that is consistent with the low values we get for quasars.“
Chemical evidence of the previous generation of high-mass Population III stars has been previously searched in stars in the Milky Way’s halo, and an initial identification was presented at least in 2014. However, Yoshii and his colleagues believe that the new results provide the clearest signature of an unstable supernova, based on the quasar’s extremely low magnesium-to-iron abundance ratio.
If this is indeed evidence of the first star and a pair of unstable supernova remnants, the discovery will help us paint a picture of how matter in the universe evolved to be what it is today, including us. To test this explanation more thoroughly, more observations are needed to determine whether other objects have similar characteristics.
But we can also find chemical signatures closer to home. Although massive Population III stars died out long ago, the chemical fingerprints they left in ejected material can last much longer and may still be around today. This means that astronomers may be able to find signatures of pair-unstable supernova explosions from distant stars that are still imprinted on objects in our local universe.
“We now know what to look for; we have a pathway,” said co-author Timothy Beers, an astronomer at the University of Notre Dame. “If this happened locally in the early universe, as it should, then we want to find evidence of it.”
 The light from this quasar has traveled for 13.1 billion years, which means astronomers are watching the object as it appeared when the universe was only 700 million years old. This corresponds to a redshift of 7.54.