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Project Progress

One of the main features of all giant planets of our solar system is the possession of irregular satellites. Distinguished from their counterparts by their highly eccentric orbits, and/or high orbital inclinations, irregular satellites are thought to have been captured from bodies that were formed elsewhere in the solar system. The accretional process of the formation of regular satellites in a circumplanetary disk cannot account for the high eccentricity and inclination of these bodies. During the past few years, observations have indicated that, (1) irregular satellites exist around all four giant planets, (2) the number of irregulars of the same size around all these planets are almost the same, and (3) there seems to be no irregular satellite in a region around Jupiter, interior to its innermost irregular (~80 Jupiter radii) and exterior to its outermost Galilean satellite (~30 Jupiter radii). During the year 7, we launched an expansive project on the study of the origins and dynamics of irregular satellites. The goal of this project is to arrive at explanations for the three above-mentioned observations. At the first stage our study focuses on identifying regions where irregular satellites can have stable orbits. We are currently carrying out extensive numerical integrations of these objects for a large parameter-space. The results of these simulations, which are to be submitted for publication shortly, will enable us to understand the lack of irregulars at the distances of 30 to 80 Jupiter-radii around this planet. We are also extending our simulations to include the scattering of small bodies with different sizes from a trans-Neptunian planetesimal disk, as a probable source of irregular satellites. The results of this project will make possible identifying the most viable capture mechanism of irregular satellites, and have applicability in furthering our understanding of outer planets formation history.