jeudi 25 octobre 2012, par Olivier Guyon (Subaru Telescope, Nat. Astr. Obs. of Japan & Steward Obs., Univ. of Arizona)
Mardi 30 octobre 2012 à 14h00 , Lieu : Salle de conférence du bât. 17
Thanks to developments in optics, large format detector arrays and computing, wide field imaging systems are becoming increasingly common in astronomy. I will illustrate how this offers new opportunities for detection and characterization of exoplanets. ASTROMETRY : Deep wide field imaging of fields around nearby stars can conceptually lead to a high precision absolute astrometric measurement, enabling detection of planets around nearby stars and measurement of their orbits and masses. At the micro-arcsecond level required for observing Earth-mass planets in habitable zones, image distortion effects are however orders of magnitude larger than the signal. I will show that these distortions can be calibrated and removed by applying small dots, covering approximately 1% of the pupil area, on the primary mirror. This allows full utilization of wide field image for astrometric measurements, offering sub-microarcsecond precision. GROUND-BASED EXOPLANET TRANSIT SURVEY : Commercial DSLR cameras offer the most cost-effective solution for obtaining high etendue (product of collecting area and field of view). They are however generally considered inappropriate for high precision photometry due to strong pixelization errors in the RGB color detector. I will show that this limitation can be overcome by data reduction, and describe our plan for a ground-based global network of low-cost DSLR-based units.
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