Gas Orbiting Young Stars

扎克曼9417158这项研究包括对星际尘埃周围可能伴随的气体的观测研究和理论分析。对围绕已知年龄的年轻恒星运行的气体的敏感研究可以为太阳系形成理论提供重要的限制，特别是涉及利用残留的行星际气体建立类木星行星的时间尺度。木星和土星很可能是由这种气体形成的，当时它被保留在太阳星云中，通常长达1000万年。这项研究的主要目标是使用最大、最灵敏的毫米波射电望远镜来测量环绕恒星运行的气体物质的质量，这些物质围绕着年龄在100万到1000万年之间的恒星运行，届时将预测到巨行星的形成。最近，已经确定了一组年龄可能在关键时间间隔内的恒星的样本，IRAM 30米射电望远镜探测到了其中许多恒星周围的分子气体。在这方面，毫米波分子光谱学是一个特别有价值的工具，因为除了测量气体质量外，它还提供了对磁盘运动学和化学的诊断。年轻目标恒星的年龄可以用各种方法来估计，例如，它在天空中相对于尘埃分子云的位置，它相对于相同温度的主序星的光度，以及它的光谱中某些关键谱线的强度。关于后者，建议的研究包括使用高分辨率的包络光谱仪测量锂、钙和氢原子的光谱线。***

Zuckerman 9417158 This research involves observational study and theoretical analysis of the gas that might accompany circumstellar disks of dust. Sensitive studies of gas orbiting young stars of known age could provide important constraints for theories of solar system formation, in particular time scales involved for the building of Jupiter-like planets from residual interplanetary gas. Jupiter and Saturn likely formed from such gas durine the time that it was retained in the solar nebula, typically up to about 10 million years. The primary objective of the study is to use the largest and most sensitive millimeter wavelength radio telescopes to measure the mass of gaseous material that orbits stars with ages between one and ten million years, when giant planet formation is predicted. Very recently, identification of a sample of stars with likely ages in the critical time interval have been identified and the IRAM 30-m radio telescope has detected molecular gas orbiting many of these stars. In this regard millimeter wavelength molecular spectroscopy is an especially valuable tool since, in addition to a measure of gas mass, it provides a diagnostic of disk kinematics and chemistry. The age of a young target star may be estimated in a variety of ways including, for example, its location in the sky relative to dusty molecular clouds, its luminosity relative to main sequence stars of the same temperature, and the strength of certain key lines in its optical spectrum. Concerning the latter, the proposed research includes measurements of optical lines of lithium, calcium, and hydrogen atoms using high resolution eschelle spectrographs. ***