A chemical signature of first-generation very massive stars

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Science  22 Aug 2014:
Vol. 345, Issue 6199, pp. 912-915
DOI: 10.1126/science.1252633

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How huge early stars enriched the universe

How big did the first generation of stars get? Knowing their size is critical to understanding how they enriched the chemistry of the universe through supernova explosions. According to numerical simulations, some of the earliest stars were more than 100 times the Sun's mass. However, no traces of these live-fast, die-young stars had been detected in any low-mass stars still extant from that era. Aoki et al. now show spectra of one such metal-poor star that may have recorded the activity of a very massive predecessor (see the Perspective by Bromm). This observational evidence will spur further supernova models, as none predicts this specific chemical signature.

Science, this issue p. 912; see also p. 868


Numerical simulations of structure formation in the early universe predict the formation of some fraction of stars with several hundred solar masses. No clear evidence of supernovae from such very massive stars has, however, yet been found in the chemical compositions of Milky Way stars. We report on an analysis of a very metal-poor star SDSS J001820.5–093939.2, which possesses elemental-abundance ratios that differ significantly from any previously known star. This star exhibits low [α-element Fe] ratios and large contrasts between the abundances of odd and even element pairs, such as scandium/titanium and cobalt/nickel. Such features have been predicted by nucleosynthesis models for supernovae of stars more than 140 times as massive as the Sun, suggesting that the mass distribution of first-generation stars might extend to 100 solar masses or larger.

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