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__NOTOC__ Kepler-11g is an exoplanet discovered in the orbit of the sunlike star Kepler-11 by the Kepler spacecraft, a NASA satellite tasked with searching for terrestrial planets. Kepler-11g is the outermost of the star's six planets. The planet orbits at a distance of nearly half the mean distance between Earth and the Sun. It completes an orbit every 118 days, placing it much further from its star than the system's inner five planets. Its estimated radius is four times that of Earth, i.e. about Neptune's size. Kepler-11g's distance from the inner planets made its confirmation more difficult than that of the inner planets, as scientists had to work to exhaustively disprove all reasonable alternatives before Kepler-11g could be confirmed.〔 The planet's discovery, along with that of the other Kepler-11 planets, was announced on February 2, 2011. According to NASA, the Kepler-11 planets form the flattest and most compact system yet discovered.〔 ==Name and discovery== Kepler-11 was originally called KOI-157 when NASA's Kepler spacecraft flagged the star for possible transit events, which exhibit tiny and roughly periodic decreases in the star's brightness are measured as it passes in front of its star as seen from Earth.〔 Kepler-11's name is incorporated into Kepler-11g's name because it is the host star. As Kepler-11g and its five sister planets were discovered and announced at the same time, its planets were sorted alphabetically by distance from the host star, starting with the letter ''b''. Because Kepler-11g was the furthest of the six, it was given the designation "g." The Kepler team's scientists conducted follow-up observations to confirm or reject the planetary nature of the detected object.〔 To do so, they used the Keck 1 telescope at the W.M. Keck Observatory in Hawaii; the Shane and Hale telescopes in California; telescopes at the WIYN (including MMT) and Whipple observatories in Arizona; Nordic Optical Telescope in the Canary Islands; the Hobby-Eberly and Harlan J. Smith telescopes in Texas; and NASA's Spitzer Space Telescope.〔 Because Kepler-11g orbits its star at a far greater distance than the inner five planets, fewer transits were observed, and radial velocity (the observation of a Doppler effect) interactions could not be easily discerned. As with the discovery of Kepler-9d, the Kepler team ran the information through numerous models to see if Kepler-11g's light curve could fit the profile of some other object, including an eclipsing binary star in the background that may have contaminated the data. The probability that Kepler-11g is not a planet but instead a false positive was determined to be 0.18%, effectively confirming its existence.〔 Kepler-11g, along with its five sister planets, were announced at a NASA press conference on February 2, 2011. The findings were published in the journal ''Nature'' a day later.〔 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「Kepler-11g」の詳細全文を読む スポンサード リンク
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