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Articles 1 - 11 of 11
Full-Text Articles in Physics
Asteroid Surfaces: The Importance Of Cohesive Forces, Keanna Jardine
Asteroid Surfaces: The Importance Of Cohesive Forces, Keanna Jardine
Electronic Theses and Dissertations
Adhesive forces play a significant role on airless bodies due to their weak gravities. Investigating adhesion at the surface of asteroids and their constituent components is vital to understanding their formation and evolution. Previous research has been done to understand the interaction of micron-sized spheres to planar surfaces and sphere-to-sphere interactions, which have been used to develop models of asteroid surfaces. Our investigation experimentally investigates adhesion through atomic force microscopy (AFM) measurements between JSC-1 simulant particles and several AFM tips, including a typical pyramidal gold tip and microspheres of sizes 2 μm and 15 μm. The samples of JSC-1 consist …
The Physical Properties And Composition Of Main-Belt Asteroids From Infrared Spectroscopy, Zoe Landsman
The Physical Properties And Composition Of Main-Belt Asteroids From Infrared Spectroscopy, Zoe Landsman
Electronic Theses and Dissertations
Asteroids are the remnants of planet formation, and as such, they represent a record of the physical and chemical conditions in the early solar system and its evolution over the past 4.6 billion years. Asteroids are relatively accessible by spacecraft, and thus may be a source of the raw materials necessary for future human exploration and settlement of space. Those on Earth-crossing orbits pose impact hazards for which mitigation strategies must be developed. For these reasons, several missions to asteroids are in progress or planned with the support of the National Aeronautics and Space Administration (NASA) and other national space …
Dynamical Formation Of Protoplanetesimals, Akbar Whizin
Dynamical Formation Of Protoplanetesimals, Akbar Whizin
Electronic Theses and Dissertations
The seeds of planetesimals that formed in the gaseous protoplanetary disk (PPD) have many barriers to overcome in their growth from millimeter to meter-sized and larger bodies. Centimeter-sized aggregates are weakly bound and self-gravity is almost non-existent so surface forces play a critical role in holding small loosely-bound rubble-piles together. Their orbital motions and effects form disk processes impart relative velocities leading to collisions so understanding the macroscopic disk environment is also necessary. To this end we analyze the dynamics of particles in Saturn's F ring as an analogue to understanding the orbital evolution of proto-planetesimals embedded in a PPD. …
Saturn's Rings: Measuring Particle Size Distributions Using Cassini Uvis Occultation Data, Tracy Becker
Saturn's Rings: Measuring Particle Size Distributions Using Cassini Uvis Occultation Data, Tracy Becker
Electronic Theses and Dissertations
Since its arrival to Saturn in 2004, the Cassini spacecraft has utilized its suite of sophisticated instruments to further our understanding of the Saturnian ring system. We analyze occultation data from Cassini's Ultraviolet Imaging Spectrograph (UVIS) in order to measure the particle size distribution and place limits on the minimum particle sizes in Saturn's rings. Throughout the ring system, particle accretion is countered by collisional and tidal disruption and Keplerian shear. Therefore, the particle size distribution of the rings is continually evolving. The presence of sub-centimeter particles, which have short lifetimes due to these processes, is indicative of ongoing dynamics …
Observations, Thermochemical Calculations, And Modeling Of Exoplanetary Atmospheres, Jasmina Blecic
Observations, Thermochemical Calculations, And Modeling Of Exoplanetary Atmospheres, Jasmina Blecic
Electronic Theses and Dissertations
This dissertation as a whole aims to provide the means to better understand hot-Jupiter planets through observing, performing thermochemical calculations, and modeling their atmospheres. We used Spitzer multi-wavelength secondary-eclipse observations to characterize planetary atmospheres. We chose targets with high signal-to-noise ratios, as their deep eclipses allow us to detect signatures of spectral features and assess planetary atmospheric structure and composition with greater certainty. Chapter 1 gives a short introduction. Chapter 2 presents the Spitzer secondary-eclipse analysis and atmospheric characterization of WASP-14b. The decrease in flux when a planet passes behind its host star reveals the planet dayside thermal emission, which, …
Spectral Study Of Asteroids And Laboratory Simulation Of Asteroid Organics, Kelsey Hargrove
Spectral Study Of Asteroids And Laboratory Simulation Of Asteroid Organics, Kelsey Hargrove
Electronic Theses and Dissertations
We investigate the spectra of asteroids at near- and mid-infrared wavelengths. In 2010 and 2011 we reported the detection of 3 ?m and 3.2-3.6 ?m signatures on (24) Themis and (65) Cybele indicative of water-ice and complex organics [1] [2] [3]. We further probed other primitive asteroids in the Cybele dynamical group and Themis family, finding diversity in the shape of their 3 ?m [4] [5] [6] and 10 ?m spectral features [4]. These differences indicated mineralogical and compositional variations within these asteroid populations. Also in the mid-infrared region we studied a larger population of asteroids belonging to the Bus …
Characterizing Exoplanet Atmospheres: From Light-Curve Observations To Radiative-Transfer Modeling, Patricio Cubillos Vallejos
Characterizing Exoplanet Atmospheres: From Light-Curve Observations To Radiative-Transfer Modeling, Patricio Cubillos Vallejos
Electronic Theses and Dissertations
Multi-wavelength transit and secondary-eclipse light-curve observations are some of the most powerful techniques to probe the thermo-chemical properties of exoplanets. Although the large planet-to-star brightness contrast and few available spectral bands produce data with low signal-to-noise ratios, a Bayesian approach can robustly reveal what constraints we can set, without over-interpreting the data. Here I performed an end-to-end analysis of transiting exoplanet data. I analyzed space-telescope data for three planets to characterize their atmospheres and refine their orbits, investigated correlated noise estimators, and contributed to the development of the respective data-analysis pipelines. Chapters 2 and 3 describe the Photometry for Orbits, …
Creation And Application Of Routines For Determining Physical Properties Of Asteroids And Exoplanets From Low Signal-To-Noise Data Sets, Nathaniel Lust
Creation And Application Of Routines For Determining Physical Properties Of Asteroids And Exoplanets From Low Signal-To-Noise Data Sets, Nathaniel Lust
Electronic Theses and Dissertations
Astronomy is a data heavy field driven by observations of remote sources reflecting or emitting light. These signals are transient in nature, which makes it very important to fully utilize every observation. This however is often difficult due to the faintness of these observations, often are only slightly above the level of observational noise. We present new or adapted methodologies for dealing with these low signal-to-noise scenarios, along with practical examples including determining exoplanet physical properties, periodicities in asteroids, and the rotational and orbital properties of the multiple asteroid system 2577 Litva.
Studying Short-Period Comets And Long-Period Comets Detected By Wise/Neowise, Emily Kramer
Studying Short-Period Comets And Long-Period Comets Detected By Wise/Neowise, Emily Kramer
Electronic Theses and Dissertations
The Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22 μm) between January 2010 and February 2011. During the mission, WISE serendipitously observed 160 comets, including 21 newly discovered objects. About 89 of the comets observed by WISE displayed a significant dust tail in the 12 and 22 μm (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both long-period comets (LPCs) and short-period comets (SPCs), differences in their activity can be used to better understand the thermal …
Detecting And Characterizing Exoplanets: The Gj 436 And Hd 149026 Systems, Kevin Stevenson
Detecting And Characterizing Exoplanets: The Gj 436 And Hd 149026 Systems, Kevin Stevenson
Electronic Theses and Dissertations
This dissertation investigates two stellar systems known to contain extrasolar planets. It is comprised of five chapters that are readily divided into three independent but related analyses. Chapter 1 reports on the analysis of low signal-to-noise secondary-eclipse observations of the Neptune-sized exoplanet GJ 436b using the Spitzer Space Telescope in multiple infrared channels. The measured wavelength-dependent eclipse depths provide constraints on the planet’s dayside atmospheric composition and thermal profile. The analysis indicates that GJ 436b’s atmosphere is abundant in carbon monoxide and deficient in methane relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere. Chapter 2 discusses the techniques …
Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille
Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille
Electronic Theses and Dissertations
The Cassini mission provided wonderful tools to explore Saturn, its satellites and its rings system. The UVIS instrument allowed stellar occultation observations of structures in the rings with the best resolution available (around 10 meters depending on geometry and navigation), bringing our understanding of the physics of the rings to the next level. In particular, we have been able to observe, dissect, model and test the interactions between the satellites and the rings. We first looked at kilometer-wide structures generated by resonances with satellites orbiting outside the main rings. The observation of structures in the C ring and their association …