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Posted by: dvandorn Jun 4 2005, 06:36 PM

I've heard some rumors recently of a new theory of Jupiter's relative position in the solar system -- something about its having formed well outside of the orbit of Saturn and having migrated in to its current position.

First, I guess I'd like to know what, if anything, y'all have heard about this theory. And are there any hard facts supporting it (such as analysis of isotopic abundances, etc.)?

I have to admit, the Saturn system shows a lot of effects of high gravity gradients occurring at some time in the past. What makes me wonder about Jupiter's pasage being responsible is that we don't see the same effects on the Jovian moons that we see on Saturn's.

I guess the question is, how would a Jovian passage so obviously disrupt the Saturn system (tearing moons apart, flinging some completely out of its orbit, placing others in far different orbits than they started in), while the four major moons of Jupiter show no such effects?

-the other Doug

Posted by: Bob Shaw Jun 4 2005, 07:29 PM

I've seen some brief reports, but I had the impression that the suggestion was that *all* the outer planets may have migrated inward.

It's not beyond the realms of the possible that after the sun went through the T-Tauri phase of it's early youth there was some sort of linkage between the massive solar wind, the solar magnetic field, the protoplanetaries and the dust disk which might have led to some momentum transfers and consequent orbital changes - but these'd happen to the whole shooting match, not just one planet.

On the other hand, we do know that something odd *did* happen in the outer solar system long after that...

...and that gravitational resonances can do odd things (Mercury-Venus-Earth, Kirkwood Gaps, Trojans, and the rest!) .

Posted by: alan Jun 4 2005, 07:35 PM

Here is the story
http://www.spaceref.com/news/viewpr.html?pid=16953
I don't believe they are claiming Jupiter crossed Saturn's orbit. The orbits started closer together, as Jupiter moved in it passed through a resonance with Saturn (two Jupiter orbits for each of Saturn's) which made their orbits more eccentric stirring up the orbits of everything nearby.

Posted by: Bob Shaw Jun 4 2005, 07:40 PM

Alan:

I'd missed that - it sounds fairly credible!

Bob Shaw

Posted by: lukemeister Jun 9 2005, 08:44 PM

I think the "other Doug" might have been referring to something else. Alan is right, the three papers that came out in Nature on May 26 dealt with a scenario in which Jupiter moved in a bit and Saturn moved out a bit. They crossed their mutual 2:1 resonance and shook up the outer solar system.

But there's another issue having to do with Jupiter's volatiles, as measured by the Galileo probe, not having the abundance pattern that had been expected by most. Noble gases, carbon, nitrogen, and sulfur are all enhanced above solar abundances by similar amounts. The simplest interpretation of this observation is that the planetesimals that formed Jupiter trapped volatiles at a temperature of only 30K, which could mean that Jupiter formed at 30 AU or beyond, the solar nebula at 5 AU was far colder than expected, or ices that formed in the parent interstellar cloud always remained cold (Owen et al., Nature 402 (1999), 269). However, Gautier, Hersant, Mousis, and Lunine [Astrophysical Journal Letters 550, (2001), pages L227–L230; erratum in ApJ Lett 559 (2001), page L183] have an alternative model that doesn't require formation of Jupiter at an extremely cold temperature. The Gautier et al. model predicts a lot of oxygen in the deep envelope of Jupiter, more than in the Owen et al. model. The just-selected Juno mission should be able to do microwave soundings to pressures of hundreds of bars in Jupiter's atmosphere, and resolving this issue is a major goal of Juno.

Posted by: ljk4-1 Oct 18 2005, 03:42 PM

Paper: astro-ph/0510479

Date: Mon, 17 Oct 2005 12:36:36 GMT (339kb)

Title: Formation of Giant Planets by Concurrent Accretion of Solids and Gas
inside an Anti-Cyclonic Vortex

Authors: Hubert Klahr (1) and Peter Bodenheimer (2) ((1)Max-Planck-Institut
fuer Astronomie, Heidelberg, (2) UCO/Lick Observatory, University of
California, Santa Cruz)

Comments: 27 pages, 4 figures, ApJ submitted
\\
We study the formation of a giant gas planet by the core--accretion
gas--capture process, with numerical simulations, under the assumption that the
planetary core forms in the center of an anti-cyclonic vortex. The presence of
the vortex concentrates particles of centimeter to meter size from the
surrounding disk, and speeds up the core formation process. Assuming that a
planet of Jupiter mass is forming at 5 AU from the star, the vortex enhancement
results in considerably shorter formation times than are found in standard
core--accretion gas--capture simulations. Also, formation of a gas giant is
possible in a disk with mass comparable to that of the minimum mass solar
nebula.

\\ ( http://arXiv.org/abs/astro-ph/0510479 , 339kb)

Posted by: ljk4-1 Oct 18 2005, 03:49 PM

Paper: astro-ph/0510487

Date: Mon, 17 Oct 2005 15:03:28 GMT (697kb)

Title: Planet formation and migration

Authors: John C B Papaloizou (DAMTP, UK) and Caroline Terquem (IAP, France)

Comments: Review to appear in Reports on Progress in Physics, 75 pages, 23
figures

We review the observations of extrasolar planets, ongoing developments in
theories of planet formation, orbital migration, and the evolution of
multiplanet systems.

\\ ( http://arXiv.org/abs/astro-ph/0510487 , 697kb)