Department of Astronomy, University of Bologna, Via Ranzani, 1, 40127 Bologna, Italy.
Nature. 2009 Nov 26;462(7272):483-6. doi: 10.1038/nature08581.
Globular star clusters are compact and massive stellar systems old enough to have witnessed the entire history of our Galaxy, the Milky Way. Although recent results suggest that their formation may have been more complex than previously thought, they still are the best approximation to a stellar population formed over a relatively short timescale (less than 1 Gyr) and with virtually no dispersion in the iron content. Indeed, only one cluster-like system (omega Centauri) in the Galactic halo is known to have multiple stellar populations with a significant spread in iron abundance and age. Similar findings in the Galactic bulge have been hampered by the obscuration arising from thick and varying layers of interstellar dust. Here we report that Terzan 5, a globular-cluster-like system in the Galactic bulge, has two stellar populations with different iron contents and ages. Terzan 5 could be the surviving remnant of one of the primordial building blocks that are thought to merge and form galaxy bulges.
球状星团是紧凑而巨大的恒星系统，它们的年龄足以见证我们银河系的整个历史。尽管最近的研究结果表明，它们的形成可能比之前想象的更为复杂，但它们仍然是对在相对较短时间内（不到 10 亿年）形成的恒星种群的最佳近似，而且铁含量几乎没有分散。事实上，在银河系晕轮中只有一个类似于星团的系统（半人马座ω）被认为具有多个恒星种群，其铁丰度和年龄存在显著差异。在银河系核球中也有类似的发现，但由于星际尘埃的厚度和变化导致了遮挡，这些发现受到了阻碍。在这里，我们报告称，银河系核球中的一个类似于球状星团的系统——Terzan 5 具有两种具有不同铁含量和年龄的恒星种群。Terzan 5 可能是原始构建块之一的幸存遗迹，这些构建块被认为会合并并形成星系核球。
