Free Astronomy Magazine November-December 2022

17 NOVEMBER-DECEMBER 2022 ASTRO PUBLISHING Deducing the quantities of each el- ement present, however, is a tricky endeavor because the brightness of a line in a spectrum depends on many other factors besides the ele- ment’s abundance. Two co-authors of the analysis, Yuzuru Yoshii and Hi- roaki Sameshima of the University of Tokyo, have tackled this problem by developing a method of using the in- tensity of wavelengths in a quasar spectrum to estimate the abundance of the elements present there. It was by using this method to analyze the quasar’s spectrum that they and their colleagues discovered the conspicu- ously low magnesium-to-iron ratio. “It was obvious to me that the super- nova candidate for this would be a pair-instability supernova of a Popu- lation III star, in which the entire star explodes without leaving any rem- nant behind,” said Yoshii. “I was de- lighted 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 ratio of magnesium to iron that agrees with the low value we derived for the quasar.” Searches for chemical evidence for a previous generation of high-mass Population III stars have been carried out before among the stars in the halo of the Milky Way and at least one tentative identification was pre- sented in 2014. Yoshii and his col- leagues, however, think the new result provides the clearest signature of a pair-instability supernova based on the extremely lowmagnesium-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 discov- ery will help to fill in our picture of how the matter in the Universe came to evolve into what it is today, includ- ing us. To test this interpretation more thoroughly, many more obser- vations are required to see if other objects have similar characteristics. But we may be able to find the chem- ical 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 as- tronomers might be able to find the signatures of pair-instability super- nova 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 as- tronomer 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.” T his artist’s impression shows a Population III star that is 300 times more massive than our Sun exploding as a pair-in- stability supernova — an all- consuming version of a supernova that has yet to be di- rectly observed. New research may have detected the after- math of one, however, in the clouds surrounding one of the most-distant quasars ever detected. [NOIRLab/NSF/AURA/ J. da Silva/Spaceengine] !