Collaborative Research: The Evolution of Magnetic Complexity in Old Sun-like Stars

首席研究员梅特卡夫和范萨德斯将采集恒星样本的偏振光谱，以评估其磁场的强度和复杂性。对于像太阳这样的恒星来说，恒星风沿着恒星的磁力线慢慢地逃逸，并在数十亿年的时间里减慢了恒星旋转的速度。这个过程被称为磁制动。缓慢的自转导致中年危机，磁场产生开始失效。恒星从活动期（强磁场，有许多耀斑，太阳黑子和爆发）切换到活动期（磁场更弱，更复杂，活动减少）。确定这些转换发生的时间和方式将提高我们对恒星年龄的理解。为了扩大参与范围，该团队计划在科罗拉多大学举办为期15周的“科学家生存技能”研讨会，并在夏威夷大学举办暑期教师研究体验活动。该团队将使用大型双筒望远镜上的波茨坦梯队偏振和光谱仪器（PEPSI）观察12颗恒星，并结合使用拉斯康布雷斯天文台的机器人梯队光谱仪网络（NRES）的同期光谱来确定活动水平。后续的详细磁场图将使用加拿大-法国-夏威夷望远镜（CFHT）上的梯队光谱偏振观测装置（ESPaDOnS）获得。由此产生的关于恒星磁场特性如何依赖于自转和中年以后的质量的限制，将对磁化恒星风的角动量损失的理论模型产生影响，使用陀螺年代学作为推断恒星年龄的技术，并将为太阳和其他行星系统的长期“空间天气”预测提供信息。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。

Principal Investigators Metcalfe and van Saders will take polarized spectra of a sample of stars to assess the strength and complexity of their magnetic fields. For stars like our Sun, the stellar wind slowly escapes along the star’s magnetic field lines and slows down the rate at which the star rotates over a period of billions of years. This process is called magnetic braking. Slowing rotation leads to a mid-life crisis and the magnetic field generation starts to fail. Stars switch from periods of activity (strong magnetic field with many flares, sunspots, and outbursts) to in-activity (weaker more complex magnetic field with reduced activity). Determining when and how these switches occur will improve our understanding of how stars age. To broaden participation the team plan to lead a 15-week "Survival Skills for Scientists" seminar at the University of Colorado and a summer Research Experience for Teachers at the University of Hawaii.The team will observe 12 stars using the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope combined with contemporaneous spectra using Las Cumbres Observatory's Network of Robotic Echelle Spectrographs (NRES) to determine the level of activity. Follow-up detailed magnetic field maps will be obtained using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) on the Canada-France-Hawaii Telescope (CFHT). The resulting constraints on how the properties of stellar magnetism depend on rotation and mass beyond middle-age will have implications for theoretical models of angular momentum loss from magnetized stellar winds, the use of gyrochronology as a technique for inferring stellar ages, and will inform predictions of long term "space weather" for the Sun and other planetary systems.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.