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Project Progress

The main focus of our research has dealt with the formation and evolution of
potentially habitable planets in a variety of astronomical settings. In the
past year, we have extended previous models of terrestrial planet growth in
several new directions. First, we used high-resolution models to better probe
the details of planet formation. Second, we extended these models to new
settings, by exploring planet formation in binary star systems, in systems
with migrating giant planets, and around low-mass stars. Several other
projects are underway, including moons of extra-solar giant planets and
tidal-orbital evolution of terrestrial planets around low-mass stars.

Accomplishments from the past year:

1. We established rough limits on the orbit of a giant planet that would allow a terrestrial planet to form in the habitable zone (Raymond 2006; Raymond, Mandell & Sigurdsson 2006; Mandell, Raymond & Sigurdsson 2007). Our list of potentially habitable systems included the Gliese 581 system, and predicted that a possibly habitable planet could exist in that system. This is more stringent than previous studies that have focused only on dynamical stability and ignored the formation process.
2. We showed that terrestrial planets can form in the habitable zone in systems with close-in giant planets (“hot Jupiters”), despite the giant planets’ migration. Habitable zone planets in hot Jupiter systems are likely to be very water-rich (Raymond, Mandell & Sigurdsson 2006; Mandell, Raymond & Sigurdsson 2007).
3. We showed that, if they form via in situ accretion, habitable planets should be rare around low-mass stars (Raymond, Scalo & Meadows 2007).
4. We further explored the details of terrestrial planet formation with high-resolution simulations, and showed that the process of water delivery is far more robust than previously thought (Raymond, Quinn & Lunine 2006, 2007).

Connections to the field of Astrobiology:

We are studying the formation, composition, and evolution of potentially
habitable planets.

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