Exoplanets
The hunt for planets outside our Solar System — called extrasolar planets, or exoplanets for short — is one of the hottest fields in present-day astronomy. Many hundred confirmed planets are known from ground-based observations, and the Kepler spacecraft recently added more than two thousand likely candidates, including Earth-like planets in the habitable zones of their stars.
Almost all these discoveries were made with indirect detection methods, such as Doppler spectroscopy (the "radial velocity" method) and transit photometry. Only a handful of planets have been imaged directly, owing to the great technological challenges and relative scarcity of massive planets in wide orbits. However, such detections deliver unique opportunities for spectral characterization of planet atmospheres, and sample an otherwise all but inaccessible parameter space in the overall planet demography.
API is involved in the SPHERE project (Spectro-Polarimetric High-contrast Exoplanet REsearch), an endeavor to build a high-contrast imaging instrument specialized for planet-hunting. Apart from the infrared instruments (IRDIS and IFS), it will feature the world's most sensitive optical imaging polarimeter, ZIMPOL, which will be used to hunt for nearby exoplanets in reflected light.
Fig. 1: High-contrast image of the nearby Sun-like star GJ 758. Its
brown-dwarf companion, visible as a white speck near the bottom of the image, was discovered with the Subaru HiCIAO instrument as part of the SEEDS survey for planets and disks. Angular differential imaging techniques were used to reveal the companion's faint signal within the bright diffraction
halo of the parent star.
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