Measuring the outcome of planetesimal formation in the Solar System

星子是行星的基石，行星形成于围绕恒星运行的圆盘状物质中。确定影响太阳系行星形成的星子的大小范围是理解行星形成过程的关键一步。在行星形成的不同阶段，出现不同大小的物体，预计星子的大小在1至1000公里之间。柯伊伯带是太阳系的一个区域，距离太阳的距离是地球的30到1000倍。太阳系的这一区域目前没有任何行星（该区域最大的物体是矮行星），自太阳系行星形成时期以来，物质基本上没有改变。测量柯伊伯带的含量有望揭示太阳系形成早期物质的分布。最近，我们测量了大小在500到10公里之间的物体的数量分布。这些大小的分布显示出与早期形成过程相一致的特征，这些过程是由圆盘中的引力不稳定性驱动的。精确确定物体大小分布的形状将揭示星子形成的细节。在这个提议中，我们要求资金继续通过探索柯伊伯带的结构来了解行星是如何形成的。我们将通过一系列技术来研究柯伊伯带天体大小的分布和这些天体的轨道：-使用望远镜（特别是维拉C.鲁宾天文台、詹姆斯韦伯太空望远镜、哈勃太空望远镜、双子座天文台、斯巴鲁望远镜和加拿大-法国-夏威夷望远镜）进行直接观测，找到更小、更遥远的天体，并测量它们的物理性质。我们现在正在开发新的“机器学习”技术，以更好地探索这些望远镜观测产生的数据集。-使用目前正在柯伊伯带巡航的美国宇航局新视野号宇宙飞船对柯伊伯带中的物体进行现场观测。我是美国宇航局新视野柯伊伯扩展任务的联合研究员，也是将任务延长到2030年的提案的联合研究员。“新视野号”提供了柯伊伯带天体的详细观测资料，揭示了它们的表面结构，这些观测结果只能用“新视野号”进行。-通过掩星探测非常小的天体（约1公里）。恒星掩星是指当有物体经过观测者和恒星之间时，恒星变暗的现象。我们测量柯伊伯带中物体的存在和大小，当它们穿过我们和遥远的恒星时，可以探测到非常小的物体。大部分研究是由研究生直接进行的，作为他们培训的一部分，并与著名的国际研究团队合作。

Planetesimals are the building blocks of planets that form in disks of material orbiting around stars.  Determining the range of sizes of the planetesimals that let to formation of planets in our solar system is critical step towards understanding how planets form.  Planetesimals are expected to between 1 and 1000 km in size with different sized objects occurring at different stages during planet formation.  The Kuiper belt is a region of the solar system that is 30 to 1000 times further from the Sun than the Earth.   This zone of the solar system does not currently have any planets (the largest objects in this zone are dwarf planets) and the material is essentially unchanged since the period of planet formation in our solar system.  Measuring the contents of the Kuiper belt  is expected to reveal the distribution of material early in our solar systems formation. Recently we have measured the distribution of number of objects with size for objects with sizes of between 500 to 10 km.  The distribution of these sizes exhibits characteristics that are consistent with the early formation process of planetesimals having been driven by gravitational instabilities in the disk.  Precise determination of shape of the distribution of object sizes will reveal the details of the planetesimal formation. In this proposal we request funds to continue to understand how planets form by exploring the structure of the Kuiper belt.  We will examine the distribution of Kuiper belt object sizes and the orbits of these objects via a set of techniques: - Direct observations using telescopes (in particular the Vera C. Rubin Observatory, James Webb Space Telescope, Hubble Space Telescope, Gemini Observatory, Subaru Telescope and Canada-France-Hawaii Telescope) to find smaller and more distant bodies and measure their physical properties.  We are now developing new 'Machine Learning' techniques to better explore the datasets created by these telescope observations.  - In-situ observations of objects in the Kuiper belt using NASA's New Horizons spacecraft which is currently cruising through the Kuiper belt.  I am a co-Investigator on NASA New Horizons Kuiper Extended Mission and co-Investigator on the proposal to extend mission operations to 2030.  New Horizons provides detailed observations of Kuiper Belt Objects that reveal the structure of their surfaces and these observations can not be made using any other facility than New Horizons. - Detection of very small bodies (about 1km) via stellar occultations. Stellar occultations are dimming of stars when an object passes between the observer and the star.  We measure the existence and size of objects in the Kuiper belt when they cross between us and the distant stars, allowing detection of very small objects. The majority of this research is conducted directly by graduate students as part of their training and in collaboration with prestigious international research teams.