Christlieb N, Bessell M S, Beers T C, Gustafsson B, Korn A, Barklem P S, Karlsson T, Mizuno-Wiedner M, Rossi S
Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany.
Nature. 2002 Oct 31;419(6910):904-6. doi: 10.1038/nature01142.
The chemical composition of the most metal-deficient stars largely reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe. They are the local relics of epochs otherwise observable only at very high redshifts; if totally metal-free ('population III') stars could be found, this would allow the direct study of the pristine gas from the Big Bang. Earlier searches for such stars found none with an iron abundance less than 1/10,000 that of the Sun, leading to the suggestion that low-mass stars could form from clouds above a critical iron abundance. Here we report the discovery of a low-mass star with an iron abundance as low as 1/200,000 of the solar value. This discovery suggests that population III stars could still exist--that is, that the first generation of stars also contained long-lived low-mass objects. The previous failure to find them may be an observational selection effect.
金属丰度最低的恒星的化学成分在很大程度上反映了它们形成时的气体成分。这些古老的恒星为恒星形成历史以及早期宇宙中化学元素的合成提供了关键线索。它们是那些在其他情况下只有在非常高的红移时才能观测到的时代的本地遗迹；如果能找到完全无金属（“第III星族”）的恒星，这将使得对来自大爆炸的原始气体进行直接研究成为可能。早期对这类恒星的搜寻没有发现铁丰度低于太阳铁丰度万分之一的恒星，这导致有人提出低质量恒星可能由高于临界铁丰度的云团形成。在此我们报告发现一颗铁丰度低至太阳值二十万分之一的低质量恒星。这一发现表明第III星族恒星可能仍然存在——也就是说，第一代恒星中也包含寿命长的低质量天体。此前未能找到它们可能是一种观测选择效应。
