Probing the Protosolar Cloud: Characterization of the Solar System’s circumstellar building blocks at the sub-micrometer scale

探测原太阳云：亚微米尺度下太阳系星周构件的表征

• 批准号: 502338012
• 负责人: Dr. Jan Leitner
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/502338012?language=en
• 关键词: Probing; Protosolar; Cloud; Characterization; Solar

All stars lose mass in the form of ionized atoms, either continuously as stellar winds, or in explosive scenarios like novae and supernovae. Around evolved stars, these atoms eventually condense into solid particles, which carry information about the condensation conditions, and the elemental and isotopic composition of the parent star itself. So-called “presolar” stardust that is found today in primitive Solar System materials (meteorites, interplanetary dust, cometary matter) was incorporated into the molecular dust and gas cloud from which the Sun and our planetary system formed some 4.57 billion years ago. Presolar grains can be distinguished from solids of Solar System origin by their highly anomalous isotopic compositions. The study of presolar dust offers not only a unique possibility for the laboratory-based investigation of material from – now extinct – stars other than the Sun; these stardust grains also represent initial building blocks of our Solar System.In this project, I will focus on the stellar origins and isotopic compositions of the rock-forming elements calcium, titanium, and iron, and how they are affected by Galactic Chemical Evolution. Investigation of the trace elements Sr, Zr, Mo, and Ba in presolar silicates and oxides will provide additional information on grain condensation, and will help to answer the question if these elements were introduced into the protosolar nebula by O-rich presolar grains, or if they were mainly provided by carbonaceous dust. Ultimately, all these studies will allow to better constrain the different types of stellar sources that contributed material to the nascent Solar System, e.g., low-mass asymptotic giant branch (AGB) stars, core-collapse supernovae, massive AGB stars, novae, other types of supernovae), and will provide a groundwork for a classification scheme for Ca and Ti isotopes. This might even provide hints for potential connections between the presolar carriers of Ca and Ti, and the isotopic compositions of calcium-aluminum-rich inclusions (CAIs), the first solids that formed in the Solar nebula.The isotopic and trace element measurements of presolar grains will be carried out by NanoSIMS ion imaging. They will be combined with resonance ionization mass spectrometry (RIMS) of Fe and trace element isotopes from suitable grains and studies by transmission electron microscopic (TEM) techniques of selected presolar silicates and oxides, to characterize their mineralogy and monitor the degree of alteration by monitoring the distribution and oxidation state of Fe. High-precision O-isotopic investigations of presolar silicate host sites will be carried out to determine their respective degrees of alteration. Samples will be characterized by scanning electron microscopy (SEM) and SEM-based energy-dispersive x-ray spectroscopy (SEM-EDS) prior to SIMS analysis to identify promising target areas.

所有的恒星都以电离原子的形式失去质量，要么以恒星风的形式持续不断地失去质量，要么以新星和超新星的爆炸形式失去质量。在进化的恒星周围，这些原子最终凝聚成固体粒子，这些粒子携带着关于凝聚条件的信息，以及母恒星本身的元素和同位素组成。今天在原始太阳系物质（陨石、行星际尘埃、彗星物质）中发现的所谓“前太阳系”星尘，是在45.7亿年前形成太阳和我们的行星系统的分子尘埃和气体云中形成的。太阳系前颗粒可以通过其高度异常的同位素组成与太阳系起源的固体区分开来。太阳前尘埃的研究不仅提供了一种独特的可能性，可以在实验室基础上研究来自太阳以外的恒星（现已灭绝）的物质；这些星尘颗粒也代表了我们太阳系的最初组成部分。在这个项目中，我将重点研究形成岩石的元素钙、钛和铁的恒星起源和同位素组成，以及它们如何受到银河化学演化的影响。对前太阳硅酸盐和氧化物中微量元素Sr、Zr、Mo和Ba的研究将提供更多关于颗粒凝结的信息，并有助于回答这些元素是由富o前太阳颗粒引入到原太阳星云中，还是主要由碳质尘埃提供的问题。最终，所有这些研究将允许更好地约束为新生太阳系提供物质的不同类型的恒星来源（例如，低质量渐近巨星分支（AGB）恒星，核心坍缩超新星，大质量AGB恒星，新星，其他类型的超新星），并将为Ca和Ti同位素的分类方案提供基础。这甚至可能为Ca和Ti的前太阳载体与富钙铝包裹体（CAIs）的同位素组成之间的潜在联系提供线索，CAIs是太阳星云中形成的第一批固体。太阳前颗粒的同位素和微量元素测量将采用纳米sims离子成像技术进行。他们将结合共振电离质谱法（RIMS）和适当颗粒的微量元素同位素，以及透射电子显微镜（TEM）技术对选定的太阳前硅酸盐和氧化物进行研究，通过监测铁的分布和氧化状态来表征其矿物学特征并监测其变化程度。将对前太阳硅酸盐寄主地点进行高精度o同位素研究，以确定其各自的蚀变程度。在SIMS分析之前，样品将通过扫描电子显微镜（SEM）和基于SEM的能量色散x射线光谱（SEM- eds）进行表征，以确定有希望的目标区域。