The earliest stars likely formed when the universe was less than 100 million years old, or less than one percent of its current age. Known as the third group, these early stars were so massive that when they died as supernovae they ripped apart themselves and scattered a unique mix of heavy elements across interstellar space. However, despite years of careful investigation by astronomers, there has not been any conclusive evidence of these ancient stars until now.
Astronomers now believe that after studying one of the most distant known quasars using the Gemini North telescope, they have discovered the blasted remnants of the first generation of stars. By using an innovative method to determine the chemical elements contained in the clouds surrounding quasars, they eventually found a very unusual composition — compared to the proportions of these elements seen in our sun, The material contains nearly nine times more iron than magnesium.
Scientists believe the most likely explanation for the striking feature is that the material was left behind by the first generation of stars, which exploded as an unstable pair of supernovae. These very powerful versions of supernova explosions have never been witnessed, but are thought to be the end of life for massive 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 counterpart to electrons. This conversion reduces the radiation pressure inside the star\allowing gravity to overcome and trigger the collapse and subsequent explosion.
Unlike other supernovae, these dramatic events do not leave behind any stellar remnants such as neutron stars or black holes, but instead eject all their material into their surroundings. There are only two ways to find evidence of them. The first is to catch a pair of unstable supernovae as they happen, an extremely unlikely scenario; the other is to find out their chemical signatures from the material they eject into interstellar space.
In their study, the astronomers looked at previous observations made by the 8.1-meter Gemini North Telescope using the Gemini Near Infrared Spectrometer (GNIRS). Spectrometers separate the light emitted by celestial bodies into different wavelengths that carry information about the elements the celestial body contains. Gemini is one of the few telescopes with the right equipment to make such observations.
Inferring the amount of each element is tricky, however, because the brightness of a line in the spectrum depends on many other factors besides the element’s abundance.
The two co-authors of the analysis, Yuzuru Yoshii and Hiroaki Sameshima from the University of Tokyo, solved this problem by developing a method that uses wavelength intensities in the spectrum of quasars 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 discovered a markedly low magnesium-to-iron ratio.
“It was clear to me that the candidate for this supernova would be a pair-instability supernova of a class III star, in which case the entire star explodes without leaving any remnants. I’m also happy that some It was surprising to find that a pair-unstable supernova of a star with a mass about 300 times that of the Sun provided a magnesium-to-iron ratio consistent with the low value we get for quasars,” Yoshii said.
Searches for chemical evidence of the previous generation of high-mass Class III stars have been carried out in stars in the Milky Way’s halo before and a preliminary identification was presented at least in 2014. However, Yoshii and his colleagues believe that the new results provide one of the clearest indications of an unstable supernova, based on the extremely low magnesium-to-iron abundance ratio present in this quasar.
If this is indeed evidence of one of the earliest stars and the remnants of a pair of unstable supernovae, the discovery could help fill in our understanding of how matter in the universe evolved to be what it is today. To test this explanation more thoroughly, more observations are needed to see if other objects share similar characteristics.
But we might also be able to find these chemical signatures closer to home. Although high-mass Type III stars died out long ago, the chemical fingerprints they left in the ejected material can last much longer and may still linger today. This means that astronomers may find that signatures of unstable supernova explosions from long-gone stars are still imprinted on objects in our local universe.
Co-author Timothy Beers, an astronomer at the University of Notre Dame, said: “We now know what to look for; we have a pathway. If this happened in the very early universe, where it should have happened, then we would expect to find it. evidence.”