Synthesis of Organic Compounds in the Late Stages of Stellar Evolution and their Connection to the Solar System
The last phase of stellar evolution from the asymptotic giant branch (AGB) to proto-planetary nebulae (PPN), to planetary nebulae (PN) represents the most active period of synthesis of organic compounds in a stars life. Both inorganic and organic molecules and solids are found to form in the circumstellar envelopes created by stellar winds. Over 60 gas-phase molecules, including rings, radicals, and molecular ions have been identified by millimeter-wave and infraed spectroscopic observations through their rotational and vibrational transitions. Infrared spectroscopic observations of emissions from the stretching andbending modes of aliphatic and aromatic compounds have revealed a continuous synthesis of organic material from the end of the AGB to PPN, to PN. These results show that complex carbonaceous compounds can be produced in a circumstellar envrionment over a period of only a few thousand years. Most interestingly, there are a number of unidentified emission features which are almost certainly carbonaceous in anture but their exact chemical composition is unknown. These include the 21 and 30 pm emission features, and the extended red emission observed in PPN and PN. Isotopic analysis of meteorites and interplanetary dust have revealed the presence of pre-solar grains similar to those formed in evolved stars. This provides a direct link between star dust and the Solar System, and raises the possibility that the early Solar System was chemically enriched by stellar ejecta.
ISM molecules ISM structure instabilities
S. Kwok
Department of Physics, University of Hong Kong, Hong Kong, China
国际会议
The 10th Asian-Pacific Regional International Astronomical Union Meeting(第十届亚洲及太平洋地区天文学大会 APRIM)
昆明
英文
136-140
2008-08-03（万方平台首次上网日期，不代表论文的发表时间）