Interesting new extrasolar-planet abstracts, from this year's 4th Astrobiology Science Conference Options

[Guest_BruceMoomaw_*]

http://abscicon2006.arc.nasa.gov/abscicon2006.html

(1) http://abscicon2006.arc.nasa.gov/agenda-session.php?sid=31 (#63): Since optically sighting extrasolar habitrable planets requires stars that are both fairly close to Earth and not so bright tht they blot out the reflected light from their nearby planets, "the easiest stars around which to image habitable worlds are early K stars within about 10 parsecs (30 light years). These generally boring and non-famous stars are less massive, fainter, slightly more chromospherically active and significantly longer-lived than the Sun. But are they good targets, biologically speaking?"

(2) http://abscicon2006.arc.nasa.gov/agenda-session.php?sid=31 (#352): It turns out that photosynthetic vegetation is actually much easier for a TPF-type mission to detect spectrally on a habitable planet of an M-type (red dwarf) star than it is for a habitable planet orbiting a Sunlike star.

(3) http://abscicon2006.arc.nasa.gov/agenda-session.php?sid=24 (#441): Simulations of the effects of a Jupier-size planet migrating all the inward through the inner part of a forming solar system to within only 0.25 AU suggest that such an event -- contrary to accepted belief -- does not prevent the formation of habitable Earth-size planets in that star's inner system: "Although the migrating Jupiter-mass planet ejects a large amount of material, a significant fraction (10-40%) of planetary embryos remain after giant planet migration. Subsequent evolution of the system results in the formation of sizable terrestrial planets, often including a planet in the Habitable Zone (HZ). Planets formed in all simulations have high water contents from vigorous radial mixing stimulated by the migrating Jupiter. The non-migrating planet clears out the outer system, and accelerates the late stages of planet formation, but planets formed in the HZ are similar in both cases." If so, this will radically revise our search strategy for the Terrestrial Planet Finder -- which, at the moment, is scheduled not even to bother looking at stars that have been previously identified as having giant planets in their inner systems.

The simulation also found that such an inward-migrating Jupiter tends to cause the formation of "3-6 Earth-mass planets interior to the migrating Jupiter, ending up inside 0.1 AU, [which] are analogous to close-in, low-mass planets recently discovered around other stars."