Dinâmica dos anéis de poeira e satélites de Urano e do anel F de Saturno
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Data
2011-02-10
Autores
Sfair, Rafael [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Os aneis and de Urano compõem um segundo sistema de aneis juntamente com os satelites Puck, Mab, Portia e Rosalind. Estes aneis são tênues e compostos por partículas microm etricas, as quais podem ser bastante perturbadas por forças não gravitacionais, como por exemplo a força de radiação solar. Simulações numericas foram utilizadas para analisar a evolução orbital de um conjunto de part culas deste sistema com raios de 1, 3, 5 e 10 m sob infl uência da força de radiação e tambem do achatamento do planeta, combinados com a perturbação gravitacional dos satelites proximos. Como esperado, a componente do arrasto de Poynting-Robertson causa o colapso da orbita, enquando um aumento na excentricidade e verificado devido a componente da radiação solar. A inclusão do achatamento do planeta evita este aumento da excentricidade e con na as partículas na região dos aneis. Encontros com os satelites causam variações no semi-eixo maior das partículas, que podem permanecer na região dos aneis ou colidir com os satelites. Para estas colisões, o resultado mais provavel e a deposição na superficie. Como este mecanismo causa a remoção de material do anel, foram investigadas fontes adicionais de partículas. Adotando um valor aproximado para o uxo de micrometeoritos na orbita de Urano, foi calculada a quantidade de material que pode ser ejetado devido a colisões com projeteis interplanetarios. Verifi cou-se que as ejeções de Mab seriam su cientes para produzir um anel com profundidade optica comparavavel as observações. Uma analise semelhante dos efeitos da radiação solar foi conduzida para a região de poeira que existe ao redor do anel F de Saturno. O amortecimento causado pelo achatamento do planeta evita as grandes variações da excentricidade, aumentando assim o tempo de vida das particulas de poeira. Alem disso, um estudo da fotometria do anel utilizando imagens...
The and rings of Uranus form a secondary ring-moon system with the satellites Puck, Mab, Portia, and Rosalind. These rings are tenuous and dominated by micrometric particles, which can be strongly disturbed by dissipative forces, such as the solar radiation pressure. We performed a numerical analysis of the orbital evolution of a sample of particles with radii of 1, 3, 5, and 10 m under the in uence of the solar radiation force and the planetary oblateness, combined with the gravitational interaction with the close satellites. As expected, the Poynting-Robertson component of the solar radiation force causes the collapse of the orbits, while the radiation pressure causes an increase in the eccentricity of the particles. The inclusion of Uranus's oblateness prevents a large variation in the eccentricity, con ning the particles in the region of the rings. The encounters with the close satellites produce variations in the semimajor axis of the particles, leading them to move inward and outward within the ring region. These particles can either remain within the region of the rings or collide with a neighbouring satellite, and the most likely result of these collisions is the deposition of particles onto the surface of these satellites. Since this mechanism tends to cause a depletion of material of the rings, we investigate additional sources for these dust particles. Adopting a rough estimative of the ux of interplanetary meteoroids at Uranus' orbit, we calculated the amount of ejecta produced by hypervelocity impacts. We found that the ejections from Mab could generate a ring with optical depth comparable with the observations. A similar analysis of the e ects of the solar radiation force was carried out for the F-ring dust band. The damping due to the Saturn's oblateness prevents the overstated changes of the eccentricity, thus it increases in the lifetime of the particles... (Complete abstract click electronic access below)
The and rings of Uranus form a secondary ring-moon system with the satellites Puck, Mab, Portia, and Rosalind. These rings are tenuous and dominated by micrometric particles, which can be strongly disturbed by dissipative forces, such as the solar radiation pressure. We performed a numerical analysis of the orbital evolution of a sample of particles with radii of 1, 3, 5, and 10 m under the in uence of the solar radiation force and the planetary oblateness, combined with the gravitational interaction with the close satellites. As expected, the Poynting-Robertson component of the solar radiation force causes the collapse of the orbits, while the radiation pressure causes an increase in the eccentricity of the particles. The inclusion of Uranus's oblateness prevents a large variation in the eccentricity, con ning the particles in the region of the rings. The encounters with the close satellites produce variations in the semimajor axis of the particles, leading them to move inward and outward within the ring region. These particles can either remain within the region of the rings or collide with a neighbouring satellite, and the most likely result of these collisions is the deposition of particles onto the surface of these satellites. Since this mechanism tends to cause a depletion of material of the rings, we investigate additional sources for these dust particles. Adopting a rough estimative of the ux of interplanetary meteoroids at Uranus' orbit, we calculated the amount of ejecta produced by hypervelocity impacts. We found that the ejections from Mab could generate a ring with optical depth comparable with the observations. A similar analysis of the e ects of the solar radiation force was carried out for the F-ring dust band. The damping due to the Saturn's oblateness prevents the overstated changes of the eccentricity, thus it increases in the lifetime of the particles... (Complete abstract click electronic access below)
Descrição
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Mecânica celeste, Análise de imagem, Image analysis
Como citar
SFAIR, Rafael. Dinâmica dos anéis de poeira e satélites de Urano e do anel F de Saturno. 2011. 170 f. Tese (doutorado) - Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, 2011.