So to determine how much of the stuff was truly interstellar—from beyond our solar system—the researchers used other isotopic clues to screen out quantities of iron-60 produced by nuclear reactions and cosmic rays.
因此,为了确定有多少物质真正的星际物质——来自我们的太阳系之外——研究人员使用其同位素线索来筛选核反应和宇宙射线产生的铁 60 的数量。