Proefschrift--Utrecht. / "Lijst van afkortingen": p. [143]-144.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Proefschrift--Utrecht. / "Lijst van afkortingen": p. [143]-144.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. Harold A. McAlister, committee chair; Todd J. Henry, Douglas R. Gies, Theo A. ten Brummelaar, Nikolaus Dietz, committee members. Electronic text ( 433 p. : ill.) : digital, PDF file. Description based on contents viewed Oct. 29, 2007. Includes bibliographical references (p. 184-194).

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 116-120). Also available on the Internet.

Six minor planets with mean motions approximately commensurable with that of Jupiter were observed photographically: (87) Sylvia, (107) Camilla, (414) Liriope, (909) Ulla and (1574) Meyer (all with ratio 9/5), and (334) Chicago (ratio 3/2). The plates were measured on a two-coordinate measuring-machine, and reduced by the method of plate constants. Orbits were derived for all except (1574) Meyer; for (334) Chicago and for (909) Ulla, two orbits were obtained for successive years, though in the former case the orbits were not accurate. The orbits of all six planets were also integrated numerically by computer, together with that of (153) Hilda, using a technique applied to the latter planet by J. Schubart. Based on the three-body problem, this applies three mutually-perpendicular components of the disturbing force to the orbital parameters, which consequently vary with time. Short-period variables are eliminated by averaging; only the longitudes of the two planets are allowed to vary, around one cycle of the commensurability. The derivatives of the orbital elements are calculated at intervals around the cycle, and their average values used in the integration. Schubart's original method neglects the orbital inclinations of both planets; this investigation extends the equations to include the inclinations. His results for (153) Hilda are reproduced, and shown not to change greatly whether the inclinations are included or omitted. For (909) Ulla, however, considerable differences are found. The results of the integrations on all seven orbits are presented in the form of graphs, covering time-intervals of 3000 years and more. The orbit of (909) Ulla was integrated twice, once taking the ratio of mean motions as 9/5, and again as 7/4. The integrations of (153) Hilda and (334) Chicago took the ratio as 3/2. All the orbits considered appear stable over long time-intervals. The perihelion advance of (334) Chicago is interrupted by long retrogressions, as noted by Schubart. The orbit of (909) Ulla shows similar, though less marked, behaviour. Both planets are somewhat removed from exact commensurability. Comparison was made between the orbits of four of the planets, derived from observations, and the orbits predicted by the numerical integrations. In most cases, the orbital parameters changed in the direction predicted but .to a greater degree, indicating that more variables affect the real orbits of the minor planets than are taken into account in this theoretical investigation.

Planetary systems around other stars have been observed to be far more diverse than what would be expected from the example of the Solar System. Exoplanets have been detected with a wide range of sizes and separations from the host star, with a range of orbital properties including large eccentricities and small inter-planet mutual inclinations. How representative these planetary systems are, however, is unclear due to detection techniques being more sensitive to planets on close orbits around the host star. It is possible therefore that a population of wide-orbit planets could be present in these systems and be evading detection. These planets may play a significant role in forming and shaping planetary systems, resulting in the architecture that is observed today. Currently, one of the major ways of inferring the presence of wide-orbit planets, besides directly detecting them, is to consider the dynamical impact they would have on known planets. In the first part of this thesis I consider how the eccentricities of known planets are affected due to long term dynamical interactions with a wide-orbit planet. I show that the eccentricity of a known planet in a system can periodically be significantly increased due to these interactions, provided that there are a total of two planets in the system. For systems with multiple known planets I show that the inner planets can protect each other against long term eccentricity perturbations from a wide-orbit planet. Following on from this investigation, I show how the inclinations of planets are affected due to long term interactions with a wide-orbit planet. Specifically, I consider how this interaction affects the probability that planetary systems are observed to transit. I find that the presence of wide-orbit planets in transiting planetary systems can help explain the so-called `Kepler-Dichotomy' which describes the apparent excess of observed single transiting systems compared with multi-planet transiting systems. Wide-orbit planets do not just dynamically interact with other planets in a system but also with small debris type bodies, akin to the Asteroid and Kuiper belts in the Solar System. In the second half of this thesis, I consider the planetary system HR8799 which is known to host four planets and two populations of debris which lie both internally and externally to the known planets. I find, through suites of N-body simulations, that a hypothetical planet in HR8799 sculpts an outer debris population that agrees more strongly with observations, compared with what would be expected by considering the known planets in isolation. Finally, for the last part of this thesis, I describe a survey that is looking to observe wide-orbit planets in close-by planetary systems directly. The observations and analysis for this survey is currently on-going, however I show preliminary results including systems with and without potential companion detections.

The technique of searching for extra-solar planetary transits is investigated. This technique, which relies on detecting the brief, shallow eclipses caused by planets passing across the line of sight to the primary star, requires high-precision time-series photometry of large numbers of stars in order to detect these statistically rare events. Observations of ~ 18000 stars in the field including the intermediate-age open cluster NGC 6819 are presented. This target field contrasts with the stellar environment surveyed by the radial velocity technique, which concentrates on the Solar neighbourhood. I present the data-reduction techniques used to obtain high-precision photometry in a semi-automated fashion for tens of thousands of stars at a time, together with an algorithm designed to search the resulting lightcurves for the transit signatures of hot Jupiter type planets. I describe simulations designed to test the detection efficiency of this algorithm and, for comparison, predict the number of transits expected from this data, assuming that hot Jupiter planets similar to HD 209458 are as common in the field of NGC 6819 as they are in the Solar neighbourhood. While no planetary transits have yet been identified, the detection of several very low amplitude eclipses by stellar companions demonstrates the effectiveness of the method. This study also indicates that stellar activity and particularly blending are significant causes of false detections. A useful additional consequence of studying this time-series photometry is the census it provides of some of the variable stars in the field. I report on the discovery of a variety of newly-discovered variables, including Algol-type detached eclipsing binaries which are likely to consist of M-dwarf stars. Further study of these stars is strongly recommended in order to help constrain models of stellar structure at the very low mass end. I conclude with a summary of this work in the context of other efforts being made in this field and recommend promising avenues of further study.

Using the Mars Atmosphere and Volatile Evolution Neutral Gas and Ion Mass Spectrometer data, we investigate the possible impact of crustal magnetic fields on the thermal structure of the Martian upper atmosphere. Our analysis reveals a clear enhancement in temperature over regions with strong crustal magnetic fields during two deep dip campaigns covering the periods of April 17-22 and September 2-8, both in 2015. Several controlling factors, such as solar EUV irradiance, relative atomic O abundance, and non-migrating tides, do not help to explain the observed temperature enhancement, and a magnetically driven scenario is favored. We evaluate the roles of several heating mechanisms that are likely modulated by the presence of crustal magnetic fields, including Joule heating, ion chemical heating, as well as electron impact heating via either precipitating solar wind electrons or locally produced photoelectrons. The respective heating rates of these mechanisms are substantially lower than the solar EUV heating rate, implying that none of them is able to interpret the observations.