Measuring the outcome of planetesimal formation in the Solar System

微行星是行星的组成部分，形成于围绕恒星运行的物质盘中。 确定在我们的太阳系中形成行星的微行星的大小范围是理解行星如何形成的关键一步。 星子的大小预计在1到1000公里之间，不同大小的物体在行星形成的不同阶段出现。 柯伊伯带是太阳系的一个区域，距离太阳比地球远30到1000倍。 太阳系的这一区域目前没有任何行星（这一区域中最大的天体是矮行星），自太阳系行星形成以来，其物质基本上没有变化。 测量柯伊伯带的内容有望揭示太阳系形成早期的物质分布。最近，我们测量了大小在500至10公里之间的物体的数量分布。 这些尺寸的分布表现出的特征是一致的，与早期形成过程中的星子已被驱动的引力不稳定性在磁盘。 精确确定天体大小分布的形状将揭示星子形成的细节。在这份提案中，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），以寻找更小和更遥远的天体，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所创建的数据集。 - 使用美国航天局的新视野号航天器对柯伊伯带的物体进行现场观测，该航天器目前正在柯伊伯带巡航。 我是美国宇航局新视野柯伊伯扩展使命的共同研究员，也是将使命操作延长到2030年的提案的共同研究员。 新视野号提供了对柯伊伯带天体的详细观测，揭示了它们表面的结构，这些观测不能使用新视野号以外的任何其他设施进行。- 通过恒星掩星探测非常小的天体（约1公里）。恒星掩星是当一个物体从观测者和星星之间经过时恒星变暗的现象。 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之间时，可以探测到非常小的物体。这项研究的大部分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.