How and where in the solar neighborhood should one look for other life-sustaining planets?
We must conduct an extensive census of mature systems to determine the orbital characteristics and gross physical properties of extrasolar planets. In particular, we need to make a complete inventory of all nearby stars to find all Jovian-mass planets, and as many Neptune-like (ice-rock) planets as possible. This will require radial velocity precision of 1 m/s or better, astrometric precision of 50 microarcseconds, and the ability to image planets a few tenths of an arcsecond from a star. The planets will be about a factor 109 fainter than the stars in reflected visible light and a factor of 106 fainter in thermal infrared emission. A survey of carefully selected samples of more distant stars will reveal the dependence of planet formation on stellar properties such as mass, heavy element abundance, angular momentum, and magnetic field, and may well tell us when in the history of the galaxy the earliest planets formed. Determination of the frequency of Earth-like planets, and whether th
