Spectro-Polarimetric High-contrast Exoplanet REsearch (VLT-SPHERE) is an adaptive optics system and coronagraphic facility at the Very Large Telescope (VLT). It provides direct imaging as well as spectroscopic and polarimetric characterization of exoplanet systems. The instrument operates in the visible and near infrared, achieving exquisite image quality and contrast over a small field of view around bright targets.
Results from SPHERE complement those from other planet finder projects, which include HARPS, CoRoT, and the Kepler Mission. The instrument was installed on Unit Telescope "Melipal" (UT3) and achieved first light in May, 2014. At the time of installation, it was the latest of a series of second generation VLT-instruments such as X-shooter, KMOS and MUSE.
Science goals.
Direct imaging of exoplanets is extremely challenging:
SPHERE is representative of a second generation of instruments devoted towards direct high-contrast imaging of exoplanets. These instruments combine extreme adaptive optics with high-efficiency coronagraphs to correct for the atmospheric turbulence at high cadence and attenuate the glare from the host star. In addition, SPHERE employs differential imaging to exploit differences between planetary and stellar light in terms of its color or polarization. Other high-contrast imaging systems that are operational include Project 1640 at the Palomar Observatory and the Gemini Planet Imager at the Gemini South Telescope. The Large Binocular Telescope, equipped with a less advanced adaptive optics system, has successfully imaged a variety of extrasolar planets.
SPHERE is targeted towards direct detection of Jupiter-sized and larger planets separated from their host stars by 5 AU or more. Detecting and characterizing a large number of such planets should offer insight into planetary migration, the hypothetical process whereby hot Jupiters, which theory indicates cannot have formed as close to their host stars as they are found, migrate inwards from where they were formed in the protoplanetary disk. It is also hypothesized that massive distant planets should be numerous; the results from SPHERE should clarify the extent to which the current observed preponderance of closely orbiting hot Jupiters represents observational bias. SPHERE observations will focus on the following types of targets: 
Results from SPHERE complement those of detection projects that use other detection methods such as radial velocity measurements and photometric transits. These projects include HARPS, CoRoT, and the Kepler Mission.
Instrument description.
SPHERE is installed on ESO's VLT Unit Telescope 3 at the Nasmyth focus. It comprises the following subsystems:
Science results.
Early results have validated the power of the SPHERE instrument, as well as presenting results that challenge existing theory.
Performance improvements.
Several projects have been proposed to improve the performance of the SPHERE instrument:
References.
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