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Originally Posted by tony873004
As Ken pointed out, the dynamical friction would have to be very strong to continuously circularize the orbits of planets that are pumping full AUs into each others perihelions and aphelions every 500 years.
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But they're not, if they're embedded in a disc. They're pumping a
momentum change for a relatively short period of time once every 500 years, but the disc acts to damp that momentum change for the
whole of those 500 years. And such planet-disc interactions can be
fierce: some simulations show Jupiter-mass objects moving from 5AU to striking the central star in the order of 100,000 years. That's a
big transfer of angular momentum.
I pulled the paper in the library at lunchtime today, but didn't copy it. However, my recollection is that the graph didn't have the resolution to show spikes in eccentricity followed by prompt damping with a time constant of a century or so.
Grant Hutchison