Organic Synthesis in the Late Stages of Stellar Evolution

对脂肪族和芳香族化合物的拉伸和弯曲模式的红外光谱观测现在在整个宇宙中都可以看到，从恒星的星周包裹层到银河系的漫射星际介质，再到遥远的星系。一些星系多达20%的能量输出是在这些波段中发射出来的。当我们回顾过去时，它们在遥远星系中的探测表明，100亿年前宇宙中就已经发生了复杂有机物的合成。对演化恒星的观测表明，在恒星演化的后期，特别是从渐近巨星分支的末端，到原行星状星云，再到行星状星云，有机物质的合成是快速的（数千年的时间尺度）和连续的。这些合成产物通过恒星风喷射到星际介质中，结果使银河系丰富了复杂的有机物。红外光谱分析表明，载体的化学结构与芳香族和脂肪族混合纳米粒子（MAON）的化学结构一致。这些结构与在陨石、土卫六表面的有机物、彗星尘埃和行星际尘埃颗粒中发现的不溶性有机物非常相似，这表明早期太阳系可能是由恒星喷射物丰富的。作为跨学科研究计划的一部分，我们将获得红外和亚毫米波天文来源的光谱观测，对最近行星任务的数据进行数据分析，并进行量子化学计算，以确定复杂有机物的振动光谱，以便与观测数据进行比较。我们的目标是确定恒星有机物的化学结构，确定它们的化学合成途径，探索它们与太阳系有机物的关系，并研究它们对原始地球的可能影响。

Infrared spectroscopic observations of the stretching and bending modes of aliphatic and aromatic compounds are now seen throughout the Universe, from the circumstellar envelopes of stars to the diffuse interstellar medium of the Milky Way Galaxy to distant galaxies. As much as 20% of the energy output of some galaxies is emitted in these bands. As we are also looking back in time, their detection in distant galaxies suggest that synthesis of complex organics has already taken place in the Universe 10 billion years ago.Observations of evolved stars have revealed a rapid (thousands year time scale) and continuous synthesis of organic materials in the late stages of stellar evolution, specifically from the end of the asymptotic giant branch, to proto-planetary nebulae, to planetary nebulae. These synthesized products are ejected into the interstellar medium through stellar winds and as a result have enriched the Galaxy with complex organics.Analysis of the infrared spectra suggests that the chemical structure of the carrier is consistent with that of mixed aromatic and aliphatic nanoparticles (MAON). These structures are very similar to those of the insoluble organic matter found in meteorites, organics on the surface of Titan, cometary dust, and interplanetary dust particles, suggesting that the early solar system may have been enriched by stellar ejecta.As part of an interdisciplinary research program, we will obtain spectroscopic observations of astronomical sources in the infrared and submm, perform data analysis of data from recent planetary missions, and undertake quantum chemistry calculations to determine the vibrational spectra of complex organics for comparison with observed data. Our goals are to identify the chemical structure of stellar organics, to determine their chemical pathways of synthesis, to explore their relationship with Solar System organics, and to investigate their possible effects on the primordial Earth.