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تسجيل مستخدم جديدSpace-borne global astrometric surveys: the hunt for extra-solar planets
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The proposed global astrometry mission {it GAIA}, recently recommended within the context of ESAs Horizon 2000 Plus long-term scientific program, appears capable of surveying the solar neighborhood within $sim$ 200 pc for the astrometric signatures of planets around stars down to the magnitude limit of $V$=17 mag, which includes late M dwarfs at 100 pc. Realistic end-to-end simulations of the GAIA global astrometric measurements have yielded first quantitative estimates of the sensitivity to planetary perturbations and of the ability to measure their orbital parameters. Single Jupiter-mass planets around normal solar-type stars appear detectable up to 150 pc ($Vle $12 mag) with probabilities $ge$ 50 per cent for orbital periods between $sim$2.5 and $sim$8 years, and their orbital parameters measured with better than 30 per cent accuracy to about 100 pc. Jupiter-like objects (same mass and period as our giant planet) are found with similar probabilities up to 100 pc.These first experiments indicate that the {it GAIA} results would constitute an important addition to those which will come from the other ongoing and planned planet-search programs. These data combined would provide a formidable testing ground on which to confront theories of planetary formation and evolution.
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