Chemical Evidence for Pair-Instability Supernova Unveiled by Scientists Studying a Highly Massive First Star

The first stars lit up the universe during the cosmic dawn and put an end to the cosmic “dark ages” that followed the Big Bang. However, its mass distribution is one of the biggest unsolved mysteries of the universe.

Numerical simulations of the formation of the first stars estimate that the mass of the first stars reached several hundred solar masses. Among them, the first stars between 140 and 260 solar masses eventually formed a binary unstable supernovae (PISNe). PISNe is quite different from normal supernovae (eg, Type II and Type Ia supernovae) and may have a unique chemical signature in the atmospheres of next-generation stars. However, no such signature has been found.

A new study led by Professor Zhao Gang of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) has identified a strange alchemy star (LAMOST J1010+2358) in the galactic halo as clear evidence of a very massive PISNe. The first stars in the early universe, based on the Large Sky Area Multi-Object Fiber Telescope Survey Spectroscopic Survey (LAMOST) and follow-up high-resolution spectroscopic observations by the Subaru Telescope. This star has been confirmed to have formed in a predominantly gaseous cloud of 260 solar masses (PISN).

The team also includes researchers from the Yunnan Observatory of the Chinese Academy of Sciences, the Japanese National Astronomical Observatory and Australia’s Monash University.

This study has been published online in nature.

The research team conducted high-resolution follow-up spectral observations of J1010+2358 using the Subaru telescope and derived abundances of more than a dozen elements. The most important characteristic of this star is the low percentage of sodium and cobalt in it. The ratio of sodium to iron is less than 1/100 of the solar energy value. This star also shows a very large variation in abundance between odd and even charge number elements, such as sodium/magnesium and cobalt/nickel.

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The discovery of J1010+2358 is direct evidence of hydrodynamic instability due to electron-positron pair production in the massive stellar evolution theory. The formation of electron-positron pairs reduces the thermal pressure within the core of a very massive star and causes partial collapse.

“It provides essential evidence for constraining the function of elementary mass in the early universe,” said Professor Zhao Gang, corresponding author of the study. “Prior to this study, no evidence of supernovae such massive stars had been found in metal-poor stars.”

Moreover, the abundance of iron in LAMOST J1010 + 2358 ((Fe/H) = -2.42) is much higher than that of the most metal-poor stars in the galactic halo, indicating that second-generation stars formed in PISN-dominated gas. Be richer in minerals than expected.

“One of the holy grails of searching for metal-poor stars is finding evidence of these early pair-instability supernovae,” said Professor Avi Loeb, former chair of the Department of Astronomy at Harvard University.

Professor Timothy Beers, Dean of Astrophysics at the University of Notre Dame, commented on the findings, “This paper presents, to my knowledge, the first definitive association of a galactic halo star with an abundance pattern originating from PISN.”