Carbon monoxide in comets

彗星中的一氧化碳

基本信息

批准号：
1945950
负责人：
Yanga Fernandez
金额：
$ 1.57万
依托单位：
The University of Central Florida Board of Trustees
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-07-01 至 2023-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1945950&HistoricalAwards=false
关键词：
Carbon monoxide comets

项目摘要

The molecule carbon monoxide (CO) is a major large part of the cloud of surrounding material, or coma, around a comet nucleus. Comet activity seen at large distances from the Sun is often caused by CO. The amount of CO can differ by up to 5 times between comets. These large differences in CO can be clues to how the comet formed or how it has changed with time. These investigators will first use a large amount of comet spectra to study the activity of CO in two bright comets - Hale-Bopp and Hyakutake - and update an existing model for CO activity in comets. They will then use this model to learn how CO is made at greater distances from the Sun, and test the model with old and new telescopic observations of comets at different distances, and other objects that are in the outer Solar System. This research serves the national interest by promoting our understanding of what gases are in comets, what the comets' structures are like, and how they formed and changed through their lifetimes. Graduate and undergraduate students at the university where the lead investigator works will be observing, reducing and analyzing the comet spectra.Carbon monoxide (CO) is a major contributor to comet comae, and often drives the activity of comets beyond 3 AU. Substantial evidence indicates that relative CO abundances can vary by factors of about 5 between comets. This variation could be an important clue to either differences in cometary formation or processing history. Gaseous emission spectra are key to unlocking mysteries of these comets, since super-volatile sublimation drives the observed cometary activity and spectra can be used to put physical and chemical constraints on nucleus models. The investigators will use a large dataset of mm-wavelength spectra of comets already in hand, and obtain new spectra with telescope time that is already secured. The project has three parts: 1) Determine excitation and collisional parameters for comae using maps of CO and other molecular emission in two bright comets (Hale-Bopp and Hyakutake), and a 1D-spherical hybrid kinetic/dusty gas hydrodynamic model. Test the model at larger heliocentric distances with new CO maps of comet 29P/Schwassmann-Wachmann 1 at about 6 AU. 2) Derive new CO production rates using the improved coma model with new data, and recalculate them for comets in the literature. 3) Study the newly-recalculated CO production rates for a group of distantly-active comets to help construct a new model of distantly-active comet nuclei. As part of this last task, the investigators will also compare the CO production rates in two long-period comets and two Centaurs to explore the importance of nucleus size and thermal evolution of CO in outer Solar System objects. Graduate and undergraduate students will be incorporated in the research to be conducted in observing, reducing and analyzing millimeter-wavelength spectroscopy of comets.

一氧化碳 (CO) 分子是彗核周围物质云或彗发的主要组成部分。在距离太阳很远的地方看到的彗星活动通常是由 CO 引起的。彗星之间的 CO 含量最多可以相差 5 倍。 CO 的这些巨大差异可以作为彗星如何形成或如何随时间变化的线索。这些研究人员将首先使用大量彗星光谱来研究两颗明亮彗星（海尔-波普彗星和百武彗星）中的 CO 活动，并更新彗星中 CO 活动的现有模型。然后，他们将使用这个模型来了解如何在距离太阳更远的地方产生二氧化碳，并通过对不同距离的彗星以及太阳系外的其他物体进行新旧望远镜观测来测试该模型。这项研究有助于我们了解彗星中的气体、彗星的结构以及它们在其生命周期中如何形成和变化，从而服务于国家利益。首席研究员工作所在大学的研究生和本科生将观察、减少和分析彗星光谱。一氧化碳 (CO) 是彗星彗发的主要贡献者，通常会导致彗星活动超过 3 个天文单位。大量证据表明，彗星之间的相对 CO 丰度可能相差约 5 倍。这种变化可能是彗星形成或处理历史差异的重要线索。气体发射光谱是解开这些彗星之谜的关键，因为超挥发性升华驱动了观测到的彗星活动，并且光谱可用于对核模型施加物理和化学约束。研究人员将使用现有的彗星毫米波长光谱的大型数据集，并利用已经确定的望远镜时间获得新的光谱。该项目分为三个部分：1) 使用两颗明亮彗星（Hale-Bopp 和 Hyakutake）中的 CO 和其他分子发射图以及一维球形混合动力学/尘埃气体流体动力学模型来确定慧发的激发和碰撞参数。使用大约 6 个天文单位的 29P/Schwassmann-Wachmann 1 彗星的新 CO 地图在更大的日心距离上测试模型。 2）使用改进的慧发模型和新数据推导新的CO生成率，并重新计算文献中的彗星。 3）研究最新重新计算的一组遥远活跃彗星的二氧化碳生成速率，以帮助构建遥远活跃彗星核的新模型。作为最后一项任务的一部分，研究人员还将比较两颗长周期彗星和两颗半人马座的二氧化碳生成速率，以探索太阳系外天体中二氧化碳的核大小和热演化的重要性。研究生和本科生将参与观测、还原和分析彗星毫米波光谱的研究。