Three-dimensional stellar physics simulations of exotic element formation

观测天文学的进步使人们能够对宇宙中存在的不同类型的丰度模式和化学指纹有一个大大扩展的了解。在对早期宇宙中形成的贫金属恒星的大型巡天观测中，经常发现具有稀有和奇异丰度模式的恒星，这些恒星丰度观测已经发展成为研究星系形成和演化以及早期宇宙学过程的重要星系考古工具。 该项目将增进我们对奇异恒星演化过程中元素如何形成并形成黑洞的超新星爆炸的理解。在大爆炸后不久形成的第一批恒星必须拥有尚未确定的不寻常的元素形成模式，这从在最贫金属和最古老的恒星中发现的一些最有趣和异常的丰度模式中可以看出。 我们的方法是基于新一代的三维模拟的湍流，流体动力学条件的元素形成。这些模拟需要加拿大计算机公司新的尼亚加拉超级计算机的令人印象深刻的计算能力，我们已经使用了今年早些时候与我们的国际团队一起执行最大的模拟湍流核心对流在一个巨大的星星。 有了这些三维模拟，我们希望能够克服目前的一维球对称恒星演化模拟，包括湍流混合只通过一个参数化模型的局限性。通过将来自核燃烧的经常激烈和充满活力的反馈以非常高的空间分辨率纳入现实的三维模拟中，在模拟运行期间的给定时间内使用整个尼亚加拉计算机的60，000个计算核心的一半，我们将生成大质量恒星对流壳湍流条件的独特天体物理模拟数据集，比如燃烧碳和氧的外壳的合并这些模拟将提供一个前所未有的细节视图，了解元素如何在星星生命的最后阶段形成，然后爆炸为超新星。 我们研究的一个重要目标将是提高我们对大爆炸后从最初的、原始的和无金属的材料形成的第一批大质量恒星的奇异条件的理解。一维模型表明，在对流氢和氦燃烧壳层的相互作用过程中，星星内部每单位时间产生的能量相当于整个星系所产生的能量，尽管当然只是很短的时间。我们的三维模拟将揭示一颗真实的星星对这种极端和充满活力的事件的反应。他们将展示在最贫金属和最古老的恒星中观察到的异常丰度模式是否以及如何起源于这些第一批恒星。这样，我们的研究将有助于解决早期宇宙中元素形成和演化的难题。

Advances in observational astronomy have enabled a greatly expanded picture of the different types of abundance patterns and chemical fingerprints that exist in the universe. In large surveys that target metal-poor stars that have formed in the early universe stars with rare and exotic abundance patterns are now frequently found. These abundance observations of stars have evolved into the important tool of galactic archeology to study the formation and evolution of galaxies, and the cosmological processes in the early universe. This project will enhance our understanding of how the elements form in the exotic stellar evolution toward black hole formation of supernova explosion. The first stars that formed shortly after the Big Bang must have possessed yet to be determined unusual modes of element formation as is evident from some of the most intriguing and anomalous abundance patterns found in the most metal-poor and oldest stars. Our approach is based on a new generation of three-dimensional simulations of the turbulent, hydrodynamic conditions of element formation. These simulations require the impressive computing power of Compute Canada's new Niagara supercomputer, that we have used earlier this year together with our international team to perform the largest simulations of turbulent core convection in a massive star. With these three-dimensional simulations we expect to be able to overcome the limitations of present-day one-dimensional spherically-symmetric stellar evolution simulations that include turbulent mixing only via a parameterized model. By including the often violent and energetic feedback from nuclear burning into realistic three-dimensional simulations at very high spatial resolution, using about one half of the entire Niagara computer's 60,000 compute cores at a given time during a simulation run, we will generate unique astrophysics simulation data sets of the turbulent conditions of convective shells in massive stars, such as the merger of a C- and O-burning shell. These simulations will provide a view of unprecedented detail on how the elements form in the final stages of a star's life before exploding as a supernova. An important goal of our research will be to improve our understanding of the exotic conditions in the first massive stars that formed after the Big Bang from the initial, pristine and metal-free material. One-dimensional models suggest that during interactions of convective H- and He-burning shells as much energy per unit time as an entire galaxy produces would be generated inside the star, although of course only for a short time. Our three-dimensional simulations will reveal how a real star would respond to such extreme and energetic events. They will show if and how the anomalous abundance patterns observed in the most metal-poor and oldest stars can originate in these first stars. In this way our research will help to solve the puzzle of element formation and evolution in the early universe.