Habitable Planets: Observational Arguments

Details Habitable Planets: Observational Arguments Habitable Planets: Observational Arguments

Dec 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aas...197.7001m&link_type=abstract

American Astronomical Society, 197th AAS Meeting, #70.01; Bulletin of the American Astronomical Society, Vol. 32, p.1514

Astronomy and Astrophysics

Astronomy

Scientific paper

Observations of extrasolar planets and protostellar disks suggest that rocky worlds form commonly around young stars. At least 8% of stars are observed to have saturn- and jupiter-mass planets within 3 AU, and more planets are likely beyond 3 AU. The mass distribution of planets rises steeply with decreasing mass (Marcy & Butler 2000), implying that more small planets form than giant ones. Elliptical, rather than circular, orbits predominate among the 35 known planets beyond 0.2 AU. New Doppler and astrometric techniques may reveal planets having masses as low as 10 Earth-masses. Protoplanetary disks surround over half of young stars, with disk masses typically over 10X that of Jupiter. Their energy distributions from IR and mm-wave observations yield dust emissivities that imply the rapid growth (within 0.1 Myr) of dust particles to millimeter size. Thus, theoretical predictions of quick growth of rocky planets is supported. One may rationally estimate that 50% of all stars form with a retinue of rocky orbiting bodies. However, a nemesis looms for the survival of earths: dynamical scattering and ejection. The ubiquity of eccentric orbits among jupiters orbiting from 0.2--3 AU suggests that gravitational scattering among planets and planetesimals is a common phenomenon (see the following presentation by H. Levison). If so, the circular orbits and survival of the lowest mass, terrestrial planets are jeopardized. We acknowledge funding from NASA, NSF, and Sun Microsystems.

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