Collaborative Research: Mapping the Supernova Polarization Landscape

超新星，或大质量恒星的爆炸，对理解至关重要，因为它们产生并分散了许多构成行星和生命的原子元素，因为它们在整个宇宙中的亮度被用来测量宇宙的膨胀。超新星（SN）的爆炸不是球形的，而是几何上复杂的现象，随着爆炸的发展，其非球形结构导致观测特征随时间的变化。丹佛大学（DU）和圣地亚哥州立大学（SDSU）之间的一项研究合作使用了一种称为光谱偏振法的观测技术来提供SNe的详细三维信息，探测无法通过地球甚至太空直接成像来解决的空间尺度。分光偏振法将探测超新星发出的光的偏振与测量该光的光谱结合起来。这些信息揭示了随着时间的推移，喷射物中密度、温度和光照模式的变化；并提供了爆炸机制和祖系统性质的线索。该项目将通过训练学生进行这些类型的观察和建模来推进未来的发现。这也将有助于培养未来多元化的STEM社区。研究人员将开发一个实践学习模块，展示两极分化的概念，直接整合到两个活动中：由DU首席研究员（PI）共同指导的DU科技营，每年将有色人种的中学女孩带到校园进行为期一周的基于发现的STEM营，以及由SDSU PI领导的广泛的外展活动。科学家们将使用超新星光谱偏振测量（SNSPOL）项目从2011年到2018年收集的数据，SNSPOL项目是现有最大的所有类型SNe的光谱偏振观测数据库，其中包括106个所有类型的SNe，其中50个在3个以上的时期被观测到。他们将用最新的建模技术来解释这些数据。观测调查正在以越来越快的速度发现超新星和相关的瞬变现象。该项目将极大地扩展现有的SNe目录，并通过光谱偏振法和定量建立每种SN类型的共同特征，从而扩大这些发现的科学影响。SNSPOL数据库中的多时期观测记录了每个SN在光球球消退时的演变，对喷出物进行了更深入的探索，并揭示了爆炸本身本质的线索。从这些数据中提取和分析最显著的光谱偏振特征将为未来的研究人员提供丰富的信息。这些结果将建立对所有类型SNe的三维性质的更全面的理解，并形成恒星爆炸模型的关键区别。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Supernovae, or the explosions of massive stars, are critical to understand, both because they produce and disperse many of the atomic elements that make up planets and life, and because their brightness throughout the Universe is used to measure the expansion of the Universe. Supernova (SN) explosions are not spherical, but rather geometrically complex phenomena, whose aspherical structures cause variations in observed characteristics over time as the explosion evolves. A research collaboration between the University of Denver (DU) and San Diego State University (SDSU) uses an observational technique called spectropolarimetry to provide detailed three-dimensional information about SNe, probing spatial scales that cannot be resolved through direct imaging from earth or even from space. Spectropolarimetry combines detection of the polarization of light from a supernova with measurement of the spectrum of that light. This information reveals the changing densities, temperatures, and illumination patterns in the ejecta over time; and gives clues to the explosion mechanisms and the nature of progenitor systems. The project will advance the future of discovery by training students in these types of observations and modeling. It will also contribute to the training of a future diverse STEM community. The investigators will develop a hands-on learning module demonstrating the concept of polarization, for direct integration into two activities: the DU SciTech camp, co-directed by the DU principal investigator (PI), which brings middle-school girls of color to campus for a week-long discovery-based STEM camp each year, and also the extensive outreach activities led by the SDSU PI. The scientists will use data collected from 2011 to 2018 by the Supernova Spectropolarimetry (SNSPOL) Project, the largest existing database of spectropolarimetric observations of SNe of all types, which includes 106 SNe of all types, with 50 observed at 3+ epochs. They will interpret these data with new state-of-the-art modeling techniques. Observational surveys are discovering supernovae and related transients at an ever-increasing rate. The project will broaden the scientific impact of these discoveries by greatly expanding the existing catalog of SNe examined with spectropolarimetry and quantitatively establishing the common signatures of each SN type. The multi-epoch observations in the SNSPOL database trace each SN’s evolution as the photosphere recedes, probing ever deeper into the ejecta and revealing clues to the very nature of the explosion itself. Extracting and analyzing the most salient spectropolarimetric features from these data will make the wealth of information they contain available to future researchers. The results will build a fuller understanding of the 3D nature of SNe of all types and form a key discriminant for stellar explosion models.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.