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| eccentricity = 0.23127363 | period = 4.614296176 yr ( d) | inclination = 34.840998° to ecliptic 34.21° to invariable plane〔 | asc_node = 173.096248° | arg_peri = 309.930328° | mean_anomaly = 78.228704° | avg_speed = 17.65 km/s | p_orbit_ref = 〔 | p_semimajor = | p_eccentricity = | p_inclination = | p_mean_motion = 78.041654 | perihelion_rate = −1.335344 | node_rate = −46.393342 | satellites = ''none'' | allsatellites = yes | dimensions = (mean)〔 | surface_area = 〔 | volume = 〔 | mass = 〔 | density = | surface_grav = ≈ 0.21 m/s² (average) 0.022 g | escape_velocity = ≈ 0.33 km/s | axial_tilt = 〔 | rotation = ()〔 | rot_velocity = | spectral_type = B-type asteroid〔〔 | magnitude = 6.49〔 to 10.65 | abs_magnitude = 4.13〔 | albedo = 0.159 (geometric)〔 | angular_size = 0.629″ to 0.171″〔 | single_temperature = ≈ 164 K ''max:'' ≈ 265 K (−8 °C) }} Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered (after Ceres), and it is one of the largest asteroids in the Solar System. With an estimated 7% of the mass of the asteroid belt, it is the third-most-massive asteroid, being 10–30% less massive than Vesta.〔 It is in diameter, somewhat smaller than Vesta. It is likely a remnant protoplanet. When Pallas was discovered by the German astronomer Heinrich Wilhelm Matthäus Olbers on 28 March 1802, it was counted as a planet, as were other asteroids in the early 19th century. The discovery of many more asteroids after 1845 eventually led to their reclassification. Pallas's surface appears to be a silicate material; the surface spectrum and estimated density resemble carbonaceous chondrite meteorites. Pallas's orbit, at 34.8°, is unusually highly inclined to the plane of the asteroid belt, and its orbital eccentricity is nearly as large as that of Pluto, making Pallas relatively inaccessible to spacecraft.〔 It was formerly considered a possible dwarf planet due to its size, but it is no longer considered such due to having significant departures from an ellipsoid.〔 == History == 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「2 Pallas」の詳細全文を読む スポンサード リンク
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