Evidence of a first-generation star that died in a “super-supernova” explosion is discovered by Gemini’s observation of a distant quasar.
Ancient chemical remnants of the first stars to light up the universe may have been discovered by astronomers. Researchers have discovered an unusual ratio of elements they believe could only have come from debris produced by the all-consuming explosion of a 300-solar-mass first-generation star using a groundbreaking analysis of an observed distant quasar by the 8.1-meter Gemini North Telescope in Hawai’i, operated by the National Science Foundation’s NOIRLab.
The first stars probably formed when the Universe was barely 100 million years old, less than 1% of its current age. These early stars, known as Population III, were so huge that when they died as supernovae, they tore apart, scattering a unique mix of heavy elements into interstellar space. However, despite painstaking research by astronomers over many years, there has been no conclusive evidence for these ancient stars so far.
Astronomers now believe they have discovered the remnants of a first-generation star explosion after studying one of the most distant known quasars using the Gemini North Telescope, one of two identical telescopes that make up the Gemini International Observatory. They discovered a very unusual composition using an innovative method to determine the chemical elements included in the clouds around the quasar – the material contained almost 10 times more iron than magnesium compared to the ratio of these elements observed in our Sun.
Scientists believe the most likely explanation for this striking feature is that the material was left behind by a first-generation star that exploded as a pair-instability supernova. These remarkably powerful versions of supernova explosions have never been observed, but are theorized as the end of life of gigantic stars with masses between 150 and 250 times that of the Sun.
Pair-instability supernova explosions occur when photons at the center of a star spontaneously transform into electrons and positrons – the positively charged homologous antimatter of the electron. This conversion reduces the radiation pressure inside the star, allowing gravity to overcome it and leading to collapse and the resulting explosion.
Unlike other supernovae, these dramatic events leave no stellar remnants, such as a
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Astronomers may have discovered the ancient chemical remnants of the first stars to light up the Universe. Using innovative analysis of a distant quasar observed by the 8.1-meter Gemini North Telescope in Hawai’i, operated by NSF’s NOIRLab, scientists have found an unusual ratio of elements that, according to them, could only have come from the debris produced by the all-consuming explosion of a 300 solar mass first-generation star. Credit: Images and videos: PROGRAM/NOIRLab/NSF/AURA, S. Brunier/Digitized Sky Survey 2, E. Slawik, J. Pollard Image processing: TA Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab) Music: Stellardrone – Airglow
For their research, the astronomers studied the results of an earlier observation taken by the Gemini North 8.1-meter telescope using the Gemini Near-Infrared Spectrograph (GNIRS). A spectrograph splits the light emitted by celestial objects into its constituent wavelengths, which contain information about the elements the objects contain. Gemini is one of the few telescopes of its size with the right equipment to perform such observations.
Deducing the amounts of each element present, however, is a tricky business because the brightness of a line in a spectrum depends on many other factors besides the abundance of the element.
Two co-authors of the analysis, Yuzuru Yoshii and Hiroaki Sameshima of the University of Tokyo, tackled this problem by developing a method using the intensity of wavelengths in a quasar spectrum to estimate the abundance elements present there. It was by using this method to analyze the quasar’s spectrum that they and their colleagues discovered the conspicuously low magnesium to iron ratio.
“It was obvious to me that the candidate supernova for this would be a pair-instability supernova of a Population III star, in which the entire star explodes without leaving a remnant,” Yoshii said. “I was delighted and somewhat surprised to find that a pair-instability supernova of a star with a mass about 300 times that of the Sun provides a magnesium to iron ratio that matches the low value we have derived for the quasar.”
Searches for chemical evidence of a previous generation of high-mass population III stars have already been conducted among stars in the halo of the
” data-gt-translate-attributes=”[{” attribute=””>Milky Way and at least one tentative identification was presented in 2014. Yoshii and his colleagues, however, think the new result provides the clearest signature of a pair-instability supernova based on the extremely low magnesium-to-iron abundance ratio presented in this quasar.
If this is indeed evidence of one of the first stars and of the remains of a pair-instability supernova, this discovery will help to fill in our picture of how the matter in the Universe came to evolve into what it is today, including us. To test this interpretation more thoroughly, many more observations are required to see if other objects have similar characteristics.
But we may be able to find the chemical signatures closer to home, too. Although high-mass Population III stars would all have died out long ago, the chemical fingerprints they leave behind in their ejected material can last much longer and may still linger on today. This means that astronomers might be able to find the signatures of pair-instability supernova explosions of long-gone stars 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 very early Universe, which it should have done, then we would expect to find evidence for it.”
Reference: “Potential Signature of Population III Pair-instability Supernova Ejecta in the BLR Gas of the Most Distant Quasar at z = 7.54*” by Yuzuru Yoshii, Hiroaki Sameshima, Takuji Tsujimoto, Toshikazu Shigeyama, Timothy C. Beers and Bruce A. Peterson, 28 September 2022, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ac8163
The study was funded by the National Science Foundation.
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