Experimental Studies of Pebble Accretion in the Protoplanetary Disk

围绕我们的太阳和其他恒星的行星的形成始于尘埃大小的颗粒粘在一起，并逐渐形成越来越大的物体。从鹅卵石大小的物体到千米尺度的物体的成长阶段可能遵循几种不同路线中的一种或多种，这取决于物体到恒星的距离和恒星的年龄。该项目将对卵石大小的尘埃、冰和岩石之间的广泛碰撞进行实验研究，以确定导致较大物体生长的条件。这些实验的结果将有助于解决有关行星形成的关键阶段的根本问题，包括水、冰和其他生物上重要的分子在粘连过程中所起的作用。许多实验将在微重力或自由落体环境中进行，以复制早期太阳系的条件。将对碰撞的视频数据进行分析，以了解行星形成早期阶段类似碰撞的结果。本科生和研究生将参与实验，视频数据将通过公共网站共享，让普通公众、学生和研究人员可视化这一行星系统历史上的关键阶段。拟议的活动是对原行星盘中低能碰撞的实验探索，以更好地了解卵石大小(厘米级)的集合体和固体的碰撞演化，这些集合体和固体是行星的最初组成部分。这些实验将通过包括混合了硅酸盐的冰粒来研究太阳系外部(水蒸气凝结的霜冻线以外)的吸积效率，并通过研究在聚集体中有和没有冰粒的大型聚集体之间以适度的撞击速度进行碰撞，从而在参数空间中扩展目前的数据库。这些鹅卵石可能通过成对碰撞吸积生长，或者参与局部引力不稳定，形成更大的千米尺度的行星体。有可能发生了这些过程的某种组合，这取决于原行星状星云中的当地条件。吸积增长模型中不确定性的一个主要来源是小物体和尘埃聚集体以预期的低速(约0.1m/S)碰撞的行为。拟议中的实验将为这些模型增加急需的数据，以帮助确定在什么条件下吸积生长可以产生小行星，以及在各种星云环境中鹅卵石之间碰撞的结果。拟议的工作将涉及一个由几名本科生和一名研究生组成的团队，负责实验的设计、操作和解释以及结果的发布。实验数据包括高速视频，将通过公共网站microgravity.Physiics.ucf.edu与K-12教育工作者和更广泛的研究社区共享。

The formation of planets around our own Sun and around other stars begins with dust-sized particles sticking together and gradually forming larger and larger objects. The stage of growth from pebble-sized objects to km-scale objects may follow one or more of several different routes, depending on the distance of the objects from the star and the age of the star. This project will experimentally study a broad range of collisions between pebble-sized clumps of dust, ice and rock to determine the conditions that lead to growth of larger objects. The results of these experiments will help resolve fundamental questions about a critical stage in planet formation, including the role that water ice and other biologically important molecules play in the sticking process. Many of the experiments will take place in a microgravity or free-fall environment in order to replicate the conditions in the early solar system. Video data of the collisions will be analyzed to understand the outcomes of similar collisions in the early stages of planet formation. Undergraduate and graduate students will participate in the experiments, and the video data will be shared through public websites, allowing the general public, students, and researchers to visualize this critical stage in the history of planetary systems.The proposed activity is an experimental exploration of low-energy collisions in the protoplanetary disk to better understand the collisional evolution of pebble-sized (cm-scale) aggregates and solids, the initial building blocks of planets. The experiments will extend the current database in parameter space by including icy particulates mixed in with silicates to study the accretion efficiency in the outer solar system (beyond the frost line where water vapor condensed) and by studying collisions between large-scale aggregates at modest impact speed both with and without ice particles in the aggregates. These pebbles may grow through pairwise collisional accretion or participate in local gravitational instabilities to form larger km-scale planetesimals. It is possible that some combination of these processes took place, depending on the local conditions in the protoplanetary nebula. A major source of uncertainty in the accretional growth model is the behavior of small objects and aggregates of dust colliding at the low speeds expected (~0.1 - 10 m/s). The proposed experiments would add much-needed data to these models to help determine the conditions under which accretional growth can produce planetesimals and the outcomes of collisions between pebbles in various nebular environments. The proposed work will involve a team of several undergraduate students and one graduate student in the design, operation, and interpretation of the experiments as well as publication of results. The experimental data consist of high speed videos that will be shared with K-12 educators and the broader research community through the public website microgravity.physics.ucf.edu.