The Gaia Satellite, White Dwarf Stars, and the Age of the Galaxy

银河系被描绘成包含四种主要的恒星群，分别是薄盘、厚盘、凸起和光晕。所有这些种群形成于80多亿年前，一定比宇宙的年龄137亿年更年轻。从这个角度来看，太阳大约有45亿年的历史。然而，这些星系人口的年龄在10亿年或20亿年之间是不确定的。如果不能更好地了解这些星系群的年龄，天文学家就无法回答有关银河系形成的基本问题。为了在这些问题上取得进展，天文学家需要改进确定恒星年龄的方法。研究人员开发了一种新技术，比以往任何技术都能更精确地确定恒星的年龄。这项技术利用了盖亚卫星的数据和高级贝叶斯统计。该项目将对安柏瑞德航空大学的物理、数学和软件工程专业的学生进行现代统计和分析方法的培训。学生将获得与国外研究人员和学生一起工作的宝贵经验。该团队包括英国伦敦帝国理工学院的统计小组和德国海德堡马克斯普朗克研究所的盖亚研究小组。该项目致力于使妇女和代表性不足的少数民族充分参与。因此，该项目将改善美国的科学、技术、工程和数学（STEM）教育。它还将有助于培养多元化和具有全球竞争力的STEM劳动力。目前，许多类型的恒星被用作年龄的代用物，但其中白矮星最有希望。白矮星的亮度直接编码了它的年龄，但这依赖于精确测量它的距离。盖亚卫星目前正在测量有史以来最精确的三角视差距离。在盖亚正在观测的约17亿颗恒星中，将有约1.5万颗白矮星在100pc内，典型的距离不确定性为1%。相比之下，目前只有两颗距离如此精确的白矮星。提议者将把这些盖亚数据与地面调查的光学和近红外光度测量相结合。他们将用他们久经考验的建模技术分析这些数据，该技术依赖于贝叶斯统计和最先进的模型成分。这些前所未有的数据和新的建模技术将使提出者能够(1)以典型的年龄精度为1%至5%得出数千颗白矮星的年龄，然后随后确定(2)盘内恒星形成的历史，(3)厚盘内恒星形成的开始和停止，以及(4)晕的平均年龄和年龄色散。

The Milky Way is pictured as containing four major populations of stars known as the thin disk, thick disk, bulge, and halo. All these populations formed more than 8 billion years ago and must be younger than about 13.7 billion years old, the age of the Universe. For perspective, the Sun is about 4.5 billion years old. Yet, the ages of each of these Galactic populations is uncertain to one or two billion years. Without better knowledge of the ages of these populations, astronomers cannot answer fundamental questions about the formation of the Galaxy. To progress on these questions, astronomers need to improve how they determine the ages of stars. The investigators developed a new technique that more precisely determines the ages of stars than any prior technique. This technique takes advantage of data from the Gaia satellite and advanced Bayesian statistics.The project will train physics, mathematics, and software engineering students at Embry Riddle Aeronautical University in modern statistical and analysis methods. The students will gain valuable experience working with researchers and students abroad. The team includes the statistics group at Imperial College in London, England, and the Gaia research group at the Max Planck Institute in Heidelberg, Germany. The project is committed to including the full participation of women and underrepresented minorities. Therefore, the project will improve Science, Technology, Engineering, and Mathematics (STEM) education in the United States. It will also contribute to a diverse and globally competitive STEM workforce.Many types of stars are presently used as age proxies, yet among them white dwarf stars hold the most promise. A white dwarf's luminosity directly encodes its age, but this relies on accurately measuring its distance. The Gaia satellite is currently measuring the most accurate and precise trigonometric parallax distances ever obtained. Among the ~1.7 billion stars that Gaia is observing, there will be ~15,000 white dwarfs within 100 pc with typical distance uncertainties 1%. This compares to only two white dwarfs with distances presently known this accurately. The proposers will combine these Gaia data with optical and near-infrared photometry from ground-based surveys. They will analyze these data with their well-tested modeling technique, which relies on Bayesian statistics and state-of-the-art model ingredients. These unprecedented data and new modeling technique will allow the proposers to (1) derive ages for thousands of white dwarfs with typical age precisions of 1 to 5%, and then subsequently determine (2) the star formation history in the disk, (3) the onset and cessation of star formation in the thick disk, and (4) the mean age and age dispersion of the halo.