Isotopic and Elemental Abundances in Stars and Planets

精确的元素和同位素丰度测量为行星、恒星和星系的形成和演化提供了一些最强有力的约束。在未来的几十年里，它们还将为太阳系外生物特征的搜索提供信息。该团队将确定类太阳恒星，低质量红矮星，亚恒星物体（褐矮星）和系外行星大气的丰度。研究小组将利用这个样本来提供关于行星演化、恒星年龄、褐矮星内部建模、行星和星星形成以及星系化学演化模型的见解。他们将进一步开发一个以工艺为基础的外展计划，用折纸制作行星的代表，他们将通过开发一个旅行天文馆来促进地区科学教育，该天文馆将访问堪萨斯农村的社区。该团队使用3.5米IRTF望远镜上的iSHELL光谱仪测量每个目标的多达13种元素的元素丰度，包括C，O，Mg和Si。此外，该团队还率先使用该仪器测量13 CO和C18 O（以及12 C16 O）的丰度，从而首次提供恒星大气中C和O的同位素丰度。已经对两颗M矮星进行了这些同位素测量;该项目的目标是将这些测量扩展到已经观测到的各种其他物体，并进一步对更多物体进行类似的观测。随着星系年龄的增长，大质量恒星和高能事件中的核合成将导致后代恒星比其前辈拥有更多的常见元素（如C和O）的重同位素。通过这些测量更好地了解银河系化学演化模型，该团队将能够从这些同位素丰度独立推断恒星年龄，以及从Mg，Si和其他常见于岩石体的元素推断行星年龄。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估而被认为值得支持。

Precise elemental and isotopic abundance measurements provide some of the strongest constraints on the formation and evolution of planets, stars, and galaxies. In the coming decades they will also inform the search for extrasolar biosignatures. This team will determine abundances of Sun-like stars, lower-mass red dwarf stars, substellar objects (brown dwarfs), and exoplanet atmospheres. The team will use this sample to provide insights on planetary evolution, stellar ages, brown dwarf interior modeling, planet and star formation, and models of galactic chemical evolution. They will further develop a craft-based outreach program to build representations of planets using origami, and they will contribute to regional science education by developing a traveling planetarium that will visit communities in rural Kansas. The team uses the iSHELL spectrograph on the 3.5m IRTF telescope to measure elemental abundances of up to 13 elements for each target, including C, O, Mg and Si. In addition, the team has pioneered the use of this instrument to measure abundances of 13CO and C18O (as well as 12C16O), thus providing isotopic abundances of C and O in stellar atmospheres for the first time. These isotopic measurements have been done for two M dwarfs; the objective of this project is to extend these measurements to a variety of other objects that have already been observed, and furthermore to make similar observations for more objects. As a galaxy ages, nucleosynthesis in massive stars and in energetic events will lead to subsequent generations of stars having more of the heavier isotopes of common elements such as C and O than their predecessors. With a galactic chemical evolution model better understood through these measurements, the team will be able to independently infer stellar ages from these isotopic abundances, as well as planetary ages from Mg, Si and other elements that are commonly found on rocky bodies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.