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Department Library

2019

Seth Pincock (Senior Thesis, December 2019, Advisor: Darin Ragozzine )

Abstract

The triple system 47171 Lempo (1999 TC36) is very unique in the Kuiper Belt (a collection of small, icy objects past the orbit of Neptune) and in the solar system: it consists of a close-proximity binary orbited by a single moon. The two bodies of the binary have nearly identical mass. Because of the unique configuration of the system, especially the close proximity of the inner binary, the orbits are complicated and cannot be modeled using Keplerian dynamics. Dr. Simon Porter of the Southwest Research Institute developed an integrator, called SPINNY (SPIN+N-bodY), in order to produce numerical solutions to the orbits of multi-body systems. I also designed several tests in order to evaluate the accuracy of SPINNY’s models. The specifics of these tests and their results are discussed in this paper.

Benjamin Proudfoot (Senior Thesis, April 2019, Advisor: Darin Ragozzine )

Abstract

The dwarf planet (136108) Haumea has an intriguing combination of unique physical properties: near-breakup spin, two regular satellites, and an unexpectedly compact collisional family. While these properties point towards formation by a collision, there is no self-consistent and reasonably probable formation hypothesis that can connect the unusually rapid spin and the low relative velocities of Haumea family members ("Haumeans"). We explore and test the proposed formation hypotheses (catastrophic collision, graze-and-merge, and satellite collision) in detail. We flexibly parameterize the properties of the collision (e.g., the collision location) and use simple models for the unique three-dimensional velocity ejection field expected from each model to generate simulated families. These are then compared to the observed Kuiper Belt Objects using Bayesian parameter inference, including a mixture model that robustly allows for interlopers from the background population. After testing our methodology, we find that the best match to the observed Haumeans is an essentially isotropic ejection field with a typical velocity of 150 m s$^{-1}$. The graze-and-merge formation hypothesis - in which Haumeans are shed due to excess angular momentum - is clearly disfavored because the observed Haumeans are not oriented in a plane. The satellite collision model is also disfavored. Including these new constraints, we present a detailed discussion of the formation hypotheses, including variations, some of which are tested. Some new hypotheses are proposed (a cratering collision and a collision where Haumea's upper layers are "missing") and scrutinized. We do not identify a satisfactory formation hypothesis, but we do propose several avenues of additional investigation. In the process of these analyses, we identify many new candidate Haumeans and dynamically confirm 7 of them as consistent with the observed family. We also confirm that Haumeans have a shallow size distribution and discuss implications for the discovery and identification of new Haumeans.

2018

Keir Ashby (Senior Thesis, April 2018, Advisor: Darin Ragozzine )

Abstract

Discovering and understanding the properties of exoplanets, or planets orbiting other stars, is one of the great scientific quests of the 21st century. Since launching in 2009, NASA’s Kepler space telescope has returned measurements for 200,000 stars along with the exoplanet candidates orbiting them. To correct for Kepler’s bias against small and/or long-period planets, we are developing an advanced computer model capable of inferring the true underlying architectures of exoplanetary systems. This Exoplanetary System Simulator, “SysSim”, generates simulated catalogs of exoplanet systems and uses Approximate Bayesian Computation over several generations to produce several estimations of the actual exoplanet population. I have produced a flowchart to help users navigate the complex code structures of SysSim. To improve the accuracy of our MES (Multiple Event Statistic) calculations, I wrote and integrated code to interpolate MES values for individual exoplanets. I have produced several plots to analyze and interpret the results of SysSim. These figures revealed that SysSim works well in determining a good estimate for exoplanet occurrence rates but we also found that individual bins have “leaking” Simulated Observed planets and that the Simulated Observed Catalog and Kepler Catalog are significantly out of balance with each other. Further work will be undergone to examine and correct these problems.

Steven Maggard (Senior Thesis, April 2018, Advisor: Darin Ragozzine )

Abstract

Thousands of asteroid-like objects reside in the Kuiper Belt Region. For accurate dynamical classification, the precision of their orbits needs rigorously tested. Using an analysis pipeline we created, we generated 30 statistically-weighted orbital clones for over 2000 Kuiper Belt Objects(KBOs). These orbits are integrated backwards in time 50 Myr. We created a database from the propagated orbits, from which we calculated the proper orbital elements for each KBO. We used the method established by Ragozzine and Brown (2007) to determine each KBOs relation to the dwarf planet Haumea. Currently, we have more than tripled the number of Haumea Family Members established by Ragozzine and Brown (2007). We conclude that other collisional families can befound using similar methods applied to Haumea and the orbital database we created.

Will Oldroyd (Senior Thesis, April 2018, Advisor: Darin Ragozzine )

Abstract

Meteorites with high specific gravities, such as irons, appear to be underrepresented in Antarctic collections over the last 40 years. This underrepresentation is in comparison with observed meteorite falls, which are believed to represent the actual population of meteorites striking Earth. Meteorites in the Antarctic ice sheet absorb solar flux, possibly leading to downward tunneling into the ice. This descent is counteracted by ice sheet flow supporting the meteorites coupled with ablation near mountain margins, which helps to force meteorites toward the surface. Meteorites that both absorb adequate thermal energy and have a high enough thermal conductivity may instead reach a shallow equilibrium depth as downward melting overcomes upward forces during the Antarctic summer. Using a pyranometer, the incoming solar flux was measured at multiple depths in two deep field sites in Antarctica, the Miller Range (2013-14) and Elephant Moraine (2016-17). Thermal and physical interactions between a variety of meteorites and their surroundings were modeled, incorporating constraints derived from the pyranometer data. We find that a typical iron meteorite traveling upward through the ice during the Antarctic summer reaches an equilibrium depth of approximately 30 cm beneath the surface. This is slightly less deep than previous estimations. The effect of snowfall on equilibrium depth in our model is minimal. The recovery of an additional population of heavy meteorites would increase our knowledge of the formation and composition of the solar system by further constraining the number of differentiated planetesimals forming in the early inner solar system.