White Dwarf Stars Under the Influence of Planets

白色矮星代表了宇宙中约97%恒星的最终进化状态，其中包括我们的太阳。 自发现以来的世纪里，它们为基础物理学、恒星演化和相互作用以及银河系恒星群的年龄提供了深入的见解。 过去十年的观察还表明，25-50%的白色矮星拥有残留的行星系统，其大气中最近吸积的金属的存在就证明了这一点。 这些被污染的白色矮星中有一小部分是由被破坏的系外行星体碎片组成的气体和尘埃盘，还有一些显示出与行星遗迹持续电磁相互作用的证据。 这些发现提供了新的可能性，以提高我们的银河系的元素历史，系外行星系统的性质，以及行星对恒星演化的影响的理解。 位于查佩尔山的北卡罗来纳州大学的一个研究小组将对银河系盖亚地图上最冷的金属污染（DZ或DAZ型）白色矮星进行光谱调查。 他们将利用他们的结果来解决从主序星推断的锂丰度与大爆炸核合成的预期之间的众所周知的冲突。 这项工作将找到新的白色矮星，可以解决这个“宇宙锂问题”，并通过太阳系陨石的古老类似物探索早期银河系元素丰度。 在与他们的教育和推广合作伙伴莫尔黑德天文馆和科学中心（MPSC）的合作下，研究人员将通过为“发射实验室”开发一个挑战，为公众带来系外行星科学的兴奋，MPSC的新互动修补空间，让游客探索从当前研究中得出的问题。银河系的元素历史目前主要从主序星的光球测量，但是这对于在相对低的温度下消耗的锂尤其不可靠。 在太阳系中，行星、小行星，特别是陨石，提供了一种推断太阳星云原始组成的替代方法。 这种方法迄今还不适用于我们的太阳系之外，但污染的白色矮星提供了一条将其扩展到其他银河系和时代的道路。 研究人员还将研究DZ和DAZ，它们通过可观测的圆盘积极地吸积行星碎片，这些圆盘通常显示与椭圆形气体圆盘的进动相关的多普勒加宽的钙发射。 该项目包括进一步发现和监测碎片盘，以帮助了解遗迹系外行星系统的形成、演变和动力学。 最后，研究人员将研究白色矮星与残留行星的电磁相互作用的证据，并探索行星和合并对白色矮星演化的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

White dwarf stars represent the final evolutionary state for ~97% of the stars in the Universe, including our own Sun. In the century since their discovery they have provided insight into fundamental physics, stellar evolution and interactions, and the ages of Galactic stellar populations. Observations across the past decade also suggest that 25-50% of white dwarfs host remnant planetary systems, as evidenced by the presence of recently accreted metals in their atmospheres. A small fraction of these polluted white dwarfs host gas and dust disks consisting of debris from disrupted exoplanetesimals, and some show evidence for ongoing electromagnetic interaction with a planetary remnant. These discoveries provide new possibilities to enhance our understanding of the elemental history of our Galaxy, the nature of exoplanetary systems, and the influence of planets on stellar evolution. A research team at the University of North Carolina at Chapel Hill will conduct a spectroscopic survey of the coolest metal-polluted (types DZ or DAZ) white dwarfs from the Gaia map of the Milky Way Galaxy. They will use their results to address a well-known conflict between lithium abundances as inferred from main-sequence stars and the expectations of Big Bang nucleosynthesis. The work will find new white dwarfs that can address this “Cosmological Lithium Problem” and explore early Galactic element abundances via ancient analogs to Solar System meteorites. In collaboration with their education and outreach partner Morehead Planetarium and Science Center (MPSC), the investigators will bring the excitement of exoplanetary science to the public by developing a challenge for the "Launch Lab," MPSC's new interactive tinkering space that lets visitors explore problems drawn from current research.The Galaxy’s elemental history is currently measured primarily from the photospheres of main-sequence stars, but this can be especially unreliable for lithium, which is consumed at relatively low temperatures. In the Solar System, planets, asteroids, and especially meteorites offer an alternate means of inferring the primordial composition of the solar nebula. This method has not hitherto been applicable outside our Solar System, but polluted white dwarfs offer a path to extend it to other Galactic systems and epochs. The researchers will also study DZs and DAZs that are actively accreting planetary debris via observable disks, which typically show Doppler-broadened calcium emission associated with the precession of an elliptical gas disk. The project includes further discovery and monitoring of debris disks to help understand the formation, evolution, and dynamics of relic exoplanetary systems. Finally, the researchers will study white dwarfs with evidence for electromagnetic interaction with a remnant planet, and explore the effects of planets and mergers on the evolution of white dwarfs.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.