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Monash Astro Seminars
3pm, Tuesday 08 September 2009; Maths, Rm. 345
Rosemary Mardling
"Determining the internal structure of extrasolar planets, and the phenomenon of retrograde planetary orbits."
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One of the big unanswered questions in astrophysics today is how giant planets form. The favoured model involves the formation of a core composed of tens of Earth masses of solid material including water ice, followed by the accretion of a massive envelope of several hundred Earth masses of dusty gas. A strong contender, at least for making massive planets, is the gravitational instability model of planet formation, a process used by Nature to form stars; such a structure is not expected to have a core.\\ One way to discern between these two models is to estimate the steepness of planets' density profiles by measuring their apsidal motion constants. For binary stars with periods short enough for the stars have significant tidal bulges, apsidal motion constants are estimated by measuring the rate of apsidal advance caused by the non-sphericity, a method which relies on the orbit being non-circular. But tides tend to circularize orbits with the result that there are very few known systems for which this can be done. \\ The situation is even more hopeless for planets *except* in the very special situation which I will describe in this talk. I will discuss my fixed-point theory of tidal evolution of short-period planets with companions and how this has been used to estimate the apsidal motion constant of a hot Jupiter with a massive companion planet. I will also discuss the recently discovered (and related) phenomenon of retrograde orbits of hot Jupiters.
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Please email all enquiries to daniel.price@sci.monash.edu.au or rosemary.mardling@sci.monash.edu.au
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