http://www.cnn.com/2006/TECH/space/0...eut/index.html

An interesting shift from earlier opinion, when it was believed that terrestrial formation would be impeded or halted by one of these roomsweepers plowing through the inner system, but now the feeling is that epistellars may drag enough iceballs from the outer system with them to assist in ocean formation.

Interesting thought.

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I'm not completely heartless, the doctor who removed it told me he'd never be able to get it all.

Title: Predicting Planets in Known Extra-Solar Planetary Systems I: Test Particle Simulations
Authors: Rory Barnes, Sean N. Raymond

Recent work has suggested that many planetary systems lie near instability. If all systems are near instability, an additional planet must exist in stable regions of well-separated extra-solar planetary systems to push these systems to the edge of stability. We examine the known systems by placing massless test particles in between the planets and integrating for 1-10 million years. We find that some systems, HD168443 and HD74156, eject nearly all test particles within 2 million years. However we find that HD37124, HD38529, and 55Cnc have large contiguous regions in which particles survive for 10 million years. These three systems, therefore, seem the most likely candidates for additional companions. Furthermore HD74156 and HD168443 must be complete and therefore radial velocity surveys should only focus on detecting more distant companions. We also find that several systems show stable regions that only exist at nonzero eccentricities.

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Title: The Search for other Earths: limits on the giant planet orbits that allow habitable terrestrial planets to form
Authors: Sean N. Raymond

Gas giant planets are far easier than terrestrial planets to detect around other stars, and are thought to form much more quickly than terrestrial planets. Thus, in systems with giant planets, the late stages of terrestrial planet formation are strongly affected by the giant planets' dynamical presence. Observations of giant planet orbits may therefore constrain the systems that can harbour potentially habitable, Earth-like planets. We present results of 460 N-body simulations of terrestrial accretion from a disk of Moon- to Mars-sized planetary embryos. We systematically vary the orbital semimajor axis of a Jupiter-mass giant planet between 1.6 and 6 AU, and eccentricity between 0 and 0.4. We find that for Sun-like stars, giant planets inside roughly 2.5 AU inhibit the growth of 0.3 Earth-mass planets in the habitable zone. If planets accrete water from volatile-rich embryos past 2-2.5 AU, then water-rich habitable planets can only form in systems with giant planets beyond 3.5 AU. Giant planets with significant orbital eccentricities inhibit both accretion and water delivery. The majority of the current sample of extra-solar giant planets appears unlikely to form habitable planets.

Read more (220kb, PDF)

http://exoplanets.org/

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`Irony` actually does mean `metal like`...