Inaug.-dis.--Heidelberg. / Lebenslauf. "Anhang. Verzeichnis der mittleren örter von 88 fixsternen für 1900.0": p. [55]-63.

In 1968, Finson and Probstein outlined a theory which could be used to analyse cometary dust tails. This theory is applied to a series of P/Halley images, obtained using the UK Schmidt Telescope. The theory is successful and shows that P/Halley underwent a series of major outbursts during early 1986. The duration of the outbursts is approximately 2 days. This value coincides with the 2.2day nuclear rotation period, estimated by other observers. The size of the dust grains varies from submicron to several hundred microns and their calculated orbital parameters indicate that a considerable fraction of the larger grains contibute to the Zodiacal Dust Cloud. A range of CCD and UK Schmidt images reveal dust features in the comae of comets P/Crommelin, P/Giacobini-Zinner and P/Halley. Intensity contours for many images exhibited a "swinging round" effect i.e. for each image there was a systematic change in the photometric axis from the central condensation outwards. This was attributed to radiation pressure effects. Astrometric images of P/Halley show sharp parabolic hoods. These hoods are discussed with reference to near-nuclear dust grain orbits. Preliminary results indicate that the rotation period of Hailey is at least a few days. Mie (1908), developed a method by which the general properties of scattering and emission by dust grains, can be used to model cometary thermal spectra. Such a method is applied to several P/Halley spectra, taken during April, 1986. The results indicate that the dust grains could be composed of both an absorbing (e.g. magnetite) and a dielectric (e.g. silicate) material. The interrelations between decaying comets and Earth-crossing asteroids are discussed. Optical and infrared observations indicate that comet P/Neujmin 1 may be a transitionary object. P/Arend-Rigaux however, is still very active, displaying a large dust coma, with anisotropic emission.

No description available.

Ulm, Univ. Diss., 2006.

Ulm, Univ., Diss., 2009.

Thesis (Ph. D.)--University of Pennsylvania, 1910. / Describes the comet discovered in October 1898 by W.R. Brooks. This comet is also known as C/1898 U1. It is not the same as the "Brooks 2 Comet" that was discovered in July 1889.

Thesis (Ph. D.)--Johns Hopkins University, 1892. / Biography.

Thesis (Ph. D.)--Johns Hopkins University, 1892. / Biography.

Thesis (Ph. D.)--University of Pennsylvania, 1910. / Describes the comet discovered in October 1898 by W.R. Brooks. This comet is also known as C/1898 U1. It is not the same as the "Brooks 2 Comet" that was discovered in July 1889.

Comets, often referred to as cosmic time capsules, serve as invaluable repositories of information from the nascent phases of our solar system. Varying significantly in size, with nuclei ranging from a few kilometers to tens of kilometers in diameter, these celestial bodies are complex, porous aggregates of organic molecules, silicate particles, and entrapped volatile gases. Their orbits, which can be categorized into the Main Belt, the Kuiper Belt, and the Oort Cloud, offer distinct insights into their origins and the early conditions of the solar system. Understanding the physical processes occurring within these nuclei is critical, particularly in the context of comet outbursts—sudden increases in brightness accompanied by the release of gas and dust. These outbursts are the consequence of intricate internal mechanisms triggered when the comet approaches the Sun, leading to the sublimation of ice and subsequent gas production. Existing theories attribute outbursts to a buildup of internal stress, often facilitated by thermodynamic factors, such as temperature and pressure gradients, or mechanical factors, such as changes in angular momentum. However, one of the least understood aspects of these celestial bodies is the interaction of heat energy with their porous structure. This study aims to shed light on this very phenomenon, focusing on how heat energy from the Sun penetrates the surface of the comet and diffuses into its sub-layers, subsequently impacting phase transitions, gas production, and ultimately, the formation of outbursts. To accomplish this, we employ a multidisciplinary approach that combines thermodynamics, heat transfer equations, and computational modeling. We introduce a novel pore network model based on percolation theory to simulate the behavior of gas within the comet’s porous structure, allowing us to probe the intricate dynamics of gas movement and pressure build-up. Our work is validated against observational data, specifically from the European Space Agency’s Rosetta mission to Comet 67P/Churyumov-Gerasimenko. Our models have yielded preliminary results that emphasize the role of the formation of a first cluster in the porous network as a critical point for outburst occurrence. Particularly for comets approaching the perihelion position, the internal pressure and temperature dynamics become increasingly complex, and our findings contribute to a nuanced understanding of these dynamics. These insights not only advance our understanding of the comet nucleus but also offer a robust theoretical framework for investigating similar phenomena in other celestial bodies.