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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, albeit over a limited field of view, superior image quality and contrast for bright targets.〔(【引用サイトリンク】url=http://www.eso.org/sci/facilities/paranal/instruments/sphere/overview.html )〕 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 June, 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.〔(【引用サイトリンク】title=First Light for SPHERE Exoplanet Imager )〕 == Science goals == Direct imaging of exoplanets is extremely challenging: # The brightness contrast between the planet and its host star typically ranges from 10−6 for hot young giant planets emitting significant amounts of near-infrared light, to 10−9 for rocky planets seen exclusively through reflected light. # The angular separation between the planet and its host star is very small. For a planet ∼10 AU from its host and tens of parsec away, the separation would be only a few tenths of an arcsec. SPHERE is representative of a second generation of instruments devoted towards direct high-contrast imaging of exoplanets. These combine advanced adaptive optics with high-efficiency coronagraphs to attenuate 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.〔(【引用サイトリンク】url=http://www.eso.org/public/news/eso1417/ )〕 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 1 to 100 AU. 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: * nearby young stellar associations which may also offer opportunities to detect low-mass planets; * stars with known planets, in particular those with long-term residuals appearing in regression analysis of their radial velocity curves which could indicate the presence of more distant companions; * the nearest stars, which would allow detecting targets with the smallest orbits, including those which shine only by reflected light; * stars with ages in the 100 Myr to 1 Gyr range. In these young systems, even the smaller planets will still be hot and radiating copiously in the infrared, enabling lower detectable masses. * SPHERE's high contrast capabilities should also enable it to be used in the study of protoplanetary discs, brown dwarfs, evolved massive stars, and to a lesser extent, in investigations of the Solar System and extragalactic 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.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spectro-Polarimetric High-Contrast Exoplanet Research」の詳細全文を読む スポンサード リンク
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