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〔 | mass= 〔 | density=〔 | surface_grav=~ m/s² | escape_velocity=~ km/s | rotation=0.3402 d (8.1655 h)〔 | axial_tilt = 96°〔 | right_asc_north_pole = 51.8 ± 0.4°〔 | declination = +10.8 ± 0.4°〔 | spectral_type=M (Tholen)〔 | magnitude = 9.25〔 to 13.17 | abs_magnitude=7.29〔 | albedo=0.19 ± 0.01 (geometrical)〔 0.073 ± 0.002 (bond)〔 | single_temperature=170–245 K〔 }} 21 Lutetia is a large asteroid in the asteroid belt of an unusual spectral type. It measures about 100 kilometers in diameter (120 km along its major axis). It was discovered in 1852 by Hermann Goldschmidt, and is named after Lutetia, the Latin name of the city that stood where Paris was later built. Lutetia has an irregular shape and is heavily cratered, with the largest impact crater reaching 45 km in diameter. The surface is geologically heterogeneous and is intersected by a system of grooves and scarps, which are thought to be fractures. It has a high average density, meaning that it is made of metal-rich rock. The ''Rosetta'' probe passed within of Lutetia in July 2010.〔 It was the largest asteroid visited by a spacecraft until the Dawn mission arrived at Vesta in July 2011. ==Discovery and exploration== Lutetia was discovered on November 15, 1852, by Hermann Goldschmidt from the balcony of his apartment in Paris.〔 A preliminary orbit for the asteroid was computed in November–December 1852 by German astronomer Georg Rümker and others.〔 In 1903, it was photographed at opposition by Edward Pickering at Harvard College Observatory. He computed an opposition magnitude of 10.8.〔 There have been two reported stellar occultations by Lutetia, observed from Malta in 1997 and Australia in 2003, with only one chord each, roughly agreeing with IRAS measurements. On July 10, 2010, the European ''Rosetta'' space probe flew by Lutetia at a minimum distance of km at a velocity of 15 kilometres per second on its way to the comet 67P/Churyumov-Gerasimenko.〔 The flyby provided images of up to 60 meters per pixel resolution and covered about 50% of the surface, mostly in the northern hemisphere.〔〔 The 462 images were obtained in 21 narrow- and broad-band filters extending from 0.24 to 1 μm.〔 Lutetia was also observed by the visible–near-infrared imaging spectrometer VIRTIS, and measurements of the magnetic field and plasma environment were taken as well.〔〔 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「21 Lutetia」の詳細全文を読む スポンサード リンク
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