Estudo da evolução dinâmica do sistema planetário HR8799 via simulações hidrodinâmicas
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Data
2021-05-27
Autores
Camporez, Evandro Luiz de Lima
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Universidade Estadual Paulista (Unesp)
Resumo
Entre mais de 3300 sistemas planetários conhecidos, o sistema HR8799 é um dos mais interessantes sistemas de planetas gigantes pois, nele contém pelo menos quatro planetas gigantes gasosos, com massas superiores à de Júpiter. Esses quatro planetas foram detectados através da técnica de imageamento direto. Estimativas sugerem que o planeta mais próximo da estrela descreve uma órbita com distância média de cerca de 16 unidades astronômicas. A órbita estimada do planeta mais externo sugere que ele se encontre a pelo menos 60 unidades astronômicas do corpo central. A grande distância orbital desses planetas até a estrela é difícil de entender. Planetas gigantes gasosos como esses devem se formar cedo, durante os primeiros milhões de anos de vida da estrela, fase na qual a estrela possui um disco gasoso circunstelar. Apenas durante essa fase esses planetas podem adquirir seus massivos envelopes de gás. Entretanto, planetas crescendo em um disco de gás interagem gravitacionalmente com esse disco. Essa interação gera troca de momento angular o qual geralmente leva o planeta a migrar em direção à estrela. Esse estudo é motivado pela seguinte questão: como os planetas do sistema HR8799 permaneceram tão longe da estrela? A principal fonte de inspiração para o modelo de formação que nós utilizamos foi a hipótese do Grand tack, que sugere a reversão na migração dos planetas gigantes gasosos do sistema solar para explicar sua estrutura atual. Nós exploramos esta ideia e testamos se um mecanismo parecido poderia fazer com que os planetas do sistema HR8799 pudessem, de alguma forma, terem se formado mais próximo de sua estrela e posteriormente migrado para suas posições atuais. Nós estudamos a evolução e estabilidade dinâmica do sistema planetário HR8799 durante a fase do disco de gás. Nosso estudo é realizado através de simulações numéricas hidrodinâmicas realizadas através do código FARGO3D. Devido às incertezas nas massas e órbitas dos planetas do sistema HR8799 nós testamos uma variedade de configurações orbitais e massas, em mais de 140 simulações numéricas. No início das nossas simulações, nós assumimos que os planetas estão completamente formados no disco. Nossos resultados mostram que a dinâmica de sistemas do tipo HR8799 é bastante complexa. A maioria das nossas simulações apresentaram instabilidade dinâmica entre os planetas durante a fase do disco de gás, resultando na ejeção de um ou mais planetas do sistema. Apenas 15% dos nossos sistemas permaneceram estáveis durante nosso tempo de integração. Entretanto, mesmo nesses casos, os planetas migraram para região interna do disco, fazendo esses sistemas inconsistentes com o sistema HR8799. Nenhuma de nossas simulações produziu um sistema verdadeiramente análogo ao sistema HR8799. A alta taxa de instabilidade dinâmica em nossas simulações e a dificuldade em se evitar a migração desses planetas para as regiões próximas à estrela sugerem que sistemas planetários similares ao HR8799 sejam raros.
Among more than 3300 known planetary systems, the HR8799 system is one of the most interesting systems of giant planets because it contains at least four gaseous giant planets, with masses greater than that of Jupiter. These four planets were detected using the direct imaging technique. Estimates suggest that the planet closest to the star describes an orbit with an average distance of about 16 astronomical units. The estimated orbit of the outermost planet suggests that it is at least 60 astronomical units from the central body. The great orbital distance of these planets to the star is difficult to understand. Gaseous giant planets like these must form early, during the star’s first million years of life, the stage in which the star has a circumstellar gaseous disk. Only during this phase can these planets acquire their massive gas envelopes. However, planets growing on a gas disk interact gravitationally with that disk. This interaction generates an exchange of angular momentum which generally leads the planet to migrate towards the star. This study is motivated by the following question: how did the planets in the HR8799 system remain so far from the star? The main source of inspiration for the formation model we used was the Grand tack hypothesis, which suggests a reversal in the migration of the gas giant planets in the solar system to explain their current structure. We explored this idea and tested whether a similar mechanism could cause the planets in the HR8799 system to have somehow formed closer to their star and subsequently migrated to their current positions. We studied the evolution and dynamic stability of the HR8799 planetary system during the gas disc phase. Our study is carried out through hydrodynamic numerical simulations carried out using the code FARGO3D. Due to uncertainties in the masses and orbits of the planets in the HR8799 system, we tested a variety of orbital and mass configurations in more than 140 numerical s imulations. At the beginning o f our simulations, we assumed that the planets are completely formed on the disk. Our results show that the dynamics of HR8799-type systems are quite complex. Most of our simulations showed dynamic instability between the planets during the gas disk phase, resulting in the ejection of one or more planets from the system. Only 15% of our systems remained stable during our integration time. However, even in these cases, the planets migrated to the inner region of the disk, making these systems inconsistent with the HR8799 system. None of our simulations has produced a system truly analogous to the HR8799 system. The high rate of dynamic instability in our simulations and the difficulty in avoiding the migration of these planets to regions close to the star suggest that planetary systems similar to HR8799 are rare.
Among more than 3300 known planetary systems, the HR8799 system is one of the most interesting systems of giant planets because it contains at least four gaseous giant planets, with masses greater than that of Jupiter. These four planets were detected using the direct imaging technique. Estimates suggest that the planet closest to the star describes an orbit with an average distance of about 16 astronomical units. The estimated orbit of the outermost planet suggests that it is at least 60 astronomical units from the central body. The great orbital distance of these planets to the star is difficult to understand. Gaseous giant planets like these must form early, during the star’s first million years of life, the stage in which the star has a circumstellar gaseous disk. Only during this phase can these planets acquire their massive gas envelopes. However, planets growing on a gas disk interact gravitationally with that disk. This interaction generates an exchange of angular momentum which generally leads the planet to migrate towards the star. This study is motivated by the following question: how did the planets in the HR8799 system remain so far from the star? The main source of inspiration for the formation model we used was the Grand tack hypothesis, which suggests a reversal in the migration of the gas giant planets in the solar system to explain their current structure. We explored this idea and tested whether a similar mechanism could cause the planets in the HR8799 system to have somehow formed closer to their star and subsequently migrated to their current positions. We studied the evolution and dynamic stability of the HR8799 planetary system during the gas disc phase. Our study is carried out through hydrodynamic numerical simulations carried out using the code FARGO3D. Due to uncertainties in the masses and orbits of the planets in the HR8799 system, we tested a variety of orbital and mass configurations in more than 140 numerical s imulations. At the beginning o f our simulations, we assumed that the planets are completely formed on the disk. Our results show that the dynamics of HR8799-type systems are quite complex. Most of our simulations showed dynamic instability between the planets during the gas disk phase, resulting in the ejection of one or more planets from the system. Only 15% of our systems remained stable during our integration time. However, even in these cases, the planets migrated to the inner region of the disk, making these systems inconsistent with the HR8799 system. None of our simulations has produced a system truly analogous to the HR8799 system. The high rate of dynamic instability in our simulations and the difficulty in avoiding the migration of these planets to regions close to the star suggest that planetary systems similar to HR8799 are rare.
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Sistema HR8799, Formação de planetas gigantes gasosos, Hipótese Grand Tack, Estabilidade dinâmica, Simulações hidrodinâmicas, Fargo3d, HR8799 system, Formation of gaseous giant planets, Grand Tack Hypothesis, Dynamic Stability, Hydrodynamic simulations, Planetas, Sistema solar, Estrelas - Observações