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

银河系被描绘成包含四个主要的恒星群体，称为薄盘，厚盘，凸起和晕。 所有这些种群都形成于80亿年前，年龄必须小于137亿年，即宇宙的年龄。 太阳的年龄大约是45亿年。 然而，这些银河系人口中每一个的年龄都是不确定的，只有10亿或20亿年。 如果没有更好地了解这些人口的年龄，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，天文学家需要改进他们确定恒星年龄的方法。 研究人员开发了一种新技术，比任何现有技术都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先进的贝叶斯统计，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合作的宝贵经验。 该团队包括英国伦敦帝国理工学院的统计组和德国海德堡马克斯普朗克研究所的盖亚研究组。 该项目致力于让妇女和代表性不足的少数群体充分参与。 因此，该项目将改善美国的科学、技术、工程和数学（STEM）教育。 它还将有助于形成一个多样化和具有全球竞争力的STEM劳动力。许多类型的恒星目前被用作年龄代理，但其中白色矮星最有希望。 一颗白色矮星的光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准确和精确的三角视差距离。 在盖亚观测到的17亿颗恒星中，将有15,000颗白色矮星在100秒差距内，典型的距离不确定性为1%。 相比之下，目前只有两颗白色矮星的距离是准确的。 提议者将联合收割机将这些盖亚数据与地面调查的光学和近红外测光结合起来。 他们将使用经过充分测试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议者能够（1）以1%至5%的典型年龄精度推导出数千颗白色矮星的年龄，然后确定（2）盘中星星的形成历史，（3）厚盘中星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.