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: M. R. S. Hawkins : Eric W. Elst, Guido Pizarro | discovered = 24 July 1979 () 〔 14 July 1996 (1996 N2) | alt_names = P/1996 N2 | mp_category = Main-belt comet 〔〔 Main-belt asteroid 〔 Themis/ Beagle family 〔 | orbit_ref = 〔 | epoch = 2012-Sep-30 (JD 2456200.5) T_jup = 3.184 | semimajor = 3.1609 AU (a) (472.66 Gm) | perihelion = 2.6499 AU (q) (395.86 Gm) | aphelion = 3.67196 AU (Q) (549.45 Gm) | eccentricity = 0.16167 | period = 5.62 yr (2052.69 d) | inclination = 1.3868° | asc_node = 160.15° | arg_peri = 132.18° | mean_anomaly = 336.84° | avg_speed = 16.64 km/s | dimensions = 3.8±0.6 km (Spitzer) 〔 | mass = | density = 1.3(?) g/cm³ 〔 | surface_grav = | escape_velocity = | rotation = 3.471 hr (0.1446 d) 〔 | spectral_type = | magnitude = 17.24 to 20.71 | abs_magnitude = 14.0 〔 15.3R (2004) 〔 15.49R (2010) 〔 | albedo = 0.05±0.02R 〔 | single_temperature = 160 K 〔 }} Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets,〔 and is the prototype of main-belt comets. Its orbit keeps it within the asteroid belt, yet it displayed a dust tail like a comet while near perihelion in 1996, 2001, and 2007. * As a comet it is formally designated 133P/Elst–Pizarro. * As an asteroid it is designated 7968 Elst–Pizarro. Elst–Pizarro was reported in 1979 as minor planet , with its image on a photographic plate being completely stellar in appearance. Its orbit remains entirely within the orbits of Mars and Jupiter, with eccentricity 0.165, typical of a minor planet in the asteroid belt. However, the images taken by Eric W. Elst and Guido Pizarro in 1996, when it was near perihelion, clearly show a cometary tail. Since this is not normal behaviour for asteroids, it is suspected that Elst–Pizarro has a different, probably icy, composition. The cometary nature of Elst–Pizarro was first discovered when a linear dust feature was observed with the ESO 1-metre Schmidt telescope at La Silla Observatory on 7 August 1996.〔(【引用サイトリンク】title=Strange Comet Discovered at ESO )〕〔 Subsequently, around the next perihelion in November 2001, the cometary activity appeared again, and persisted for 5 months.〔 At present, there are only four other objects that are cross-listed as both comets and asteroids: 2060 Chiron (95P/Chiron), 4015 Wilson–Harrington (107P/Wilson-Harrington), 60558 Echeclus (174P/Echeclus), and 118401 LINEAR (176P/LINEAR, previously ).〔 As a dual status object, astrometric observations of 7968 Elst–Pizarro should be reported under the minor planet designation.〔 It most recently came to perihelion on 8 February 2013.〔 == References == 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「7968 Elst–Pizarro」の詳細全文を読む スポンサード リンク
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