Gas Orbiting Young Stars

Zuckerman 9417158这项研究涉及对可能伴随着尘埃盘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进行敏感的研究，可以为太阳系形成理论提供重要的限制，特别是从残留的行星际气体中建造类似彗星的行星所涉及的时间尺度。 木星和土星很可能是由这些气体在太阳星云中保留的时间形成的，通常长达1000万年。 这项研究的主要目标是使用最大和最灵敏的毫米波射电望远镜来测量围绕年龄在100万年到1000万年之间的恒星运行的气态物质的质量，预测巨型行星的形成。 最近，已经确定了一个可能年龄在临界时间间隔内的恒星样本，IRAM 30米射电望远镜探测到分子气体绕其中许多恒星运行。 在这方面，毫米波长分子光谱是一个特别有价值的工具，因为除了测量气体质量，它提供了一个诊断磁盘的运动学和化学。 年轻目标星星的年龄可以通过多种方式来估算，例如，它在天空中相对于尘埃分子云的位置，相对于相同温度的主序星的光度，以及光谱中某些关键线的强度。 关于后者，拟议的研究包括使用高分辨率埃歇尔光谱仪测量锂、钙和氢原子的光学谱线。 ***

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. ***