Dynamics of the Kuiper Belt: From Planetesimal Formation to Planetary Migration

柯伊伯带的动力学：从星子形成到行星迁移

• 批准号: 0507805
• 负责人: Eugene Chiang
• 金额: --
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-01-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0507805&HistoricalAwards=false
• 关键词: Dynamics; Kuiper; Belt; Planetesimal; Formation

AST 0507805ChiangThe Edgeworth-Kuiper Belt of planetesimals, of which Pluto is the largest known member,furnishes a grand ensemble of test particles whose trajectories reflect the chronology of events in our planetary system. The intellectual merit of Dr Eugene Chiang's research project is that it will detail three different chapters in this history: (1) The formation of planetesimals. Self-gravitational collapse of a dense layer of particles at the midplane of the protoplanetary disk promises to form superkilometer-sized objects from dust grains. Numerical hydrodynamical simulations of turbulencetriggered by the Kelvin-Helmholtz instability in this dense layer will be performed to assess whether the turbulent stress exerted by gas on dust can transport dust to regions of ever increasingmetallicity. Such regions are ripe for planetesimal formation by gravitational instability. (2) Theaccretion of planets from planetesimals. New insights into the formation environment of Neptuneare promised from the recent discovery of Neptune Trojans. Theoretical calculations, ranging from detailed order-of-magnitude estimates to numerical explorations with a new collisional Nbody code, will determine whether observed Neptune Trojans were inserted directly by collisions or grew in situ from smaller bodies. These two formation channels paint dramatically different portraits of the planetesimal disk at the time of Neptune's birth. The first places the bulk of the disk mass into objects dozens of kilometers across, while the second does the same for centimeter-sized objects. (3) The evolution of orbits. Can the Kuiper Belt's enormous dispersion of orbital inclinations be understood by appealing to ancient close encounters with Neptune? This hypothesis is valid only if the perihelia of scattered objects can subsequently be raised beyond Neptune's reach. The ability of secular resonances to raise perihelia will be tested, for the first time, in the presence of a self-gravitating disk of planetesimals. If Neptune's migration were responsible for capturing Kuiper Belt objects into low-order resonances, what demands does this process make on the mass spectrum of planetesimals which exchange angular momentum with the planet? The degree of stochasticity in planetary migration will be measured using analytic calculations and numerical experiments designed to test analytic scalings. How are high-order resonances filled by planetary migration? The potential of n:1 resonances to diagnose Neptune's ancient migration rate will be assessed, in anticipation of future all-sky astrometric surveys of the Kuiper Belt.The research has several broader impacts. Scientifically, issues of planetary migrationand resonance capture impact extrasolar planetary systems, particularly debris disk systemsthat exhibit non-axisymmetries attributed to gravitational sculpting by planets, and resonantpairs of planets such as GJ876a+b. Furthermore, understanding the requirements of planetesimalformation determines our expectation for the sizes of planetary systems, sizes that may bemeasured with future adaptive optics imaging of young extrasolar systems. From the perspectiveof human resources, Dr. Chiang will train two graduate students and a cadre of undergraduate research assistants, will teach new graduate and undergraduate classes in the physics of planetary systems, with emphasis on recently discovered Neptune-mass giants, and will continue to deliver lectures at research institutions and at public venues.***

AST 0507805 Chiang埃奇奥-柯伊伯带的星子，其中冥王星是最大的已知成员，拥有一个宏大的测试粒子系综，其轨迹反映了我们行星系统中事件的年表。尤金蒋博士的研究项目的智力价值是，它将详细介绍这段历史中的三个不同章节：（1）星子的形成。在原行星盘的中平面上，一层致密的粒子的自引力坍缩有望从尘埃颗粒中形成超光速飞行器大小的物体。将对这一致密层中Kelvin-Helmholtz不稳定性引发的湍流进行数值流体动力学模拟，以评估气体对尘埃施加的湍流应力是否能将尘埃输送到金属含量不断增加的区域。这样的区域是由引力不稳定性形成微行星的成熟区域。(2)行星由微行星吸积而成。最近发现的海王星特洛伊行星为我们提供了有关海王星形成环境的新见解。理论计算，从详细的数量级估计到新的碰撞Nbody代码的数值探索，将确定观察到的海王星特洛伊木马是直接通过碰撞插入还是从较小的物体原位生长。这两个形成通道描绘了海王星诞生时星子盘的截然不同的肖像。第一种方法将大部分的盘质量放入直径几十公里的物体中，而第二种方法对厘米大小的物体也是如此。(3)轨道的演化。柯伊伯带轨道倾角的巨大分散可以通过吸引古代与海王星的近距离接触来理解吗？这个假设只有在散射天体的近日点可以被提升到海王星的范围之外时才成立。长期共振提高近日点的能力将首次在存在自引力小行星盘的情况下进行测试。如果海王星的迁移负责捕获柯伊伯带物体进入低阶共振，这个过程对与行星交换角动量的星子的质谱有什么要求？行星迁移的随机性程度将使用分析计算和旨在测试分析标度的数值实验来测量。高阶共振是如何被行星迁移填满的？在未来对柯伊伯带进行全天空天体测量调查的预期中，将评估n：1共振诊断海王星古代迁移率的潜力。从科学上讲，行星迁移和共振捕获的问题会影响太阳系外的行星系统，特别是碎片盘系统，这些系统表现出非轴对称性，归因于行星的引力雕刻，以及GJ 876 a +B等行星的共振对。此外，了解行星形变的要求决定了我们对行星系统大小的期望，这些大小可以用未来年轻太阳系外系统的自适应光学成像来测量。在人力资源方面，江博士将培养两名研究生和一批本科生研究助理，教授新的研究生和本科生行星系统物理课程，重点是最近发现的海王星质量的巨人，并将继续在研究机构和公共场所发表演讲。