Formation of Glass with Embedded Metal and Sulfides from Shock-accelerated Crystalline Dust in Superbubbles
Formation of Glass with Embedded Metal and Sulfides from Shock-accelerated Crystalline Dust in Superbubbles
复制标题
超级气泡中冲击加速结晶粉尘形成嵌入金属和硫化物的玻璃
DOI：
10.1086/425574
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
J. Bradley
中科院分区：
文献类型：
--
作者：
A. Westphal;J. Bradley
行星际尘埃颗粒（IDP）含有神秘的亚微米成分，称为GEMS（嵌入金属和硫化物的玻璃）。GEMS的成分和结构表明，它们是通过暴露于电离辐射处理的，但实际辐照环境的细节仍然难以捉摸。在这里，我们提出了一个机制和天体物理学网站的GEMS形成，解释了第一次以下关键性质的GEMS：他们是化学计量丰富的氧和系统贫化的S，Mg，Ca和Fe（相对于太阳丰度）;大多数具有正常的（太阳）氧同位素组成;它们表现出惊人的窄尺寸分布（直径0.1-0.5 μm）;其中一些在其硅酸盐玻璃基质中含有“残余”晶体。我们发现，残余晶体的成分，尺寸分布和生存是不一致的扩散冲击加速粒子加速非晶化。相反，我们认为GEMS是由晶体颗粒形成的，这些颗粒在OB协会中的大质量恒星的恒星流出物中凝结，在与相关超级气泡（SB）内频繁的超新星冲击的相遇中加速，并在SB内部注入来自热气体的原子。因此，我们颠倒了目标和射弹的通常角色。而不是在休息时被高能离子轰击，颗粒被加速和轰击的原子束，在他们的休息框架。Meyer、Drury和Ellison提出，银河宇宙射线（GCR）来自于这些加速的尘埃颗粒溅射出的离子。我们认为，GEMS是构成GCR长期寻求的源材料的快速谷物人口的幸存成员。因此，GCR源材料的代表可能在过去30年中一直在宇宙尘埃实验室等待发现。
Interplanetary dust particles (IDPs) contain enigmatic submicron components called GEMS (glass with embedded metal and sulfides). The compositions and structures of GEMS indicate that they have been processed by exposure to ionizing radiation, but details of the actual irradiation environment(s) have remained elusive. Here we propose a mechanism and astrophysical site for GEMS formation that explains for the first time the following key properties of GEMS: they are stoichiometrically enriched in oxygen and systematically depleted in S, Mg, Ca, and Fe (relative to solar abundances); most have normal (solar) oxygen isotopic compositions; they exhibit a strikingly narrow size distribution (0.1-0.5 μm diameter); and some of them contain "relict" crystals within their silicate glass matrices. We show that the compositions, size distribution, and survival of relict crystals are inconsistent with amorphization by particles accelerated by diffusive shock acceleration. Instead, we propose that GEMS are formed from crystalline grains that condense in stellar outflows from massive stars in OB associations, are accelerated in encounters with frequent supernova shocks inside the associated superbubble (SB), and are implanted with atoms from the hot gas in the SB interior. We thus reverse the usual roles of target and projectile. Rather than being bombarded at rest by energetic ions, grains are accelerated and bombarded by a nearly monovelocity beam of atoms as viewed in their rest frame. Meyer, Drury, and Ellison have proposed that Galactic cosmic rays (GCRs) originate from ions sputtered from such accelerated dust grains. We suggest that GEMS are surviving members of a population of fast grains that constitute the long-sought source material for GCRs. Thus, representatives of the GCR source material may have been awaiting discovery in cosmic dust labs for the last 30 yr.