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Planet Hunting: Exploration and research at the leading edge of high-contrast imaging

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Search for extrasolar planets in high-contrast images

Direct imaging of planets orbiting other stars is technically challenging, but highly rewarding. A combination of the best telescopes, dedicated science instruments and sophisticated image processing techniques makes this possible.

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The PLANET HUNTING (Planet hunting: Exploration and research at the leading edge of high-contrast imaging) project conducted a direct imaging survey for planets around binary stars. It also took part in the commissioning and first scientific use of the direct imaging facility at the European Southern Observatory’s (ESO) Very Large Telescope in Chile. Both the observation schedule and the commissioning of the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) coronagraph were delayed in the first year, resulting in the need to restructure some of the project plan. The first year was therefore chiefly dedicated to completing and publishing an in-depth direct imaging study of the LkCa 15 protoplanetary disk. In the second year, the project was granted 40 hours of observation time on the newly available SPHERE subsystem Infrared Dual Imager and Spectrograph (IRDIS) planet finder facility. This included covering 40 new exploratory targets as well as several follow-up targets to complete previous survey work. These observations continued throughout much of 2015. While evaluation, follow-up and publication of these new data continue, one instantly publishable discovery has been made. A previously unknown disk structure was imaged around the close binary AK Sco, which is used as a benchmark system in stellar astrophysics. Science verification observations of LkCa 15 with the Zurich Imaging Polarimeter (ZIMPOL) confirmed the findings of a previous paper and revealed the inner disk in scattered light for the first time. Furthermore, observations of MWC 758 with ZIMPOL revealed new structures inwards of the known spiral arms. Commissioning data on AU Microscopii reveal large-scale wave-like disk features that can be traced over timescales of up to four years and appear to be moving outwards at limitless speeds. No comparable phenomenon is known from other targets or from theoretical predictions, making the interpretation challenging. A relevant paper has been accepted for publication in Nature. A preview of the results was also presented at the Spirit of Lyot conference in June 2015. An invited talk was given at the Exoplanets with JWST-MIRI conference in Heidelberg in September 2014. A report was also presented on the SPHERE team’s direct imaging activities at the PlanetS NCCR meeting in Anzère in January 2015. In addition, a contributed talk on LkCa 15 results was given at the Spirit of Lyot conference in Montreal in June 2015.


Extrasolar planets, PLANET HUNTING, direct imaging, LkCa 15, protoplanetary disk

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