7968 Elst–Pizarro
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7968 Elst–Pizarro imaged at La Silla Observatory in August 1996. The narrow tail is visible.
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| Discovery | |
|---|---|
| Discovered by | 1979 OW7: M. R. S. Hawkins R. H. McNaught,[1] S. J. Bus [2] 1996 N2: Eric W. Elst, Guido Pizarro |
| Discovery date | 24 July 1979 (1979 OW7) [3] 14 July 1996 (1996 N2) |
| Designations | |
| P/1996 N2 1979 OW7 |
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| Main-belt comet [4][5] Main-belt asteroid [6] Themis/ Beagle family [4] |
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| Orbital characteristics[6] | |
| Epoch 2012-Sep-30 (JD 2456200.5) T_jup = 3.184 |
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| Aphelion | 3.67196 AU (Q) (549.45 Gm) |
| Perihelion | 2.6499 AU (q) (395.86 Gm) |
| 3.1609 AU (a) (472.66 Gm) | |
| Eccentricity | 0.16167 |
| 5.62 yr (2052.69 d) | |
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Average orbital speed
|
16.64 km/s |
| 336.84° | |
| Inclination | 1.3868° |
| 160.15° | |
| 132.18° | |
| Physical characteristics | |
| Dimensions | 3.8±0.6 km (Spitzer) [7] |
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Mean density
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1.3(?) g/cm³ [8] |
| 3.471 hr (0.1446 d) [6] | |
| Albedo | 0.05±0.02R [7] |
| Temperature | 160 K [8] |
| 17.24 to 20.71 | |
| 14.0 [6] 15.3R (2004) [8] 15.49R (2010) [9] |
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Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets,[10] 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 1979 OW7, 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.[8][11]
Subsequently, around the next perihelion in November 2001, the cometary activity appeared again, and persisted for 5 months.[8]
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 1999 RE70).[12] As a dual status object, astrometric observations of 7968 Elst–Pizarro should be reported under the minor planet designation.[12]
It most recently came to perihelion on 8 February 2013.[6]
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found. (older 2010 site)
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 6.0 6.1 6.2 6.3 6.4 Lua error in package.lua at line 80: module 'strict' not found. Archived from the original on 2012-08-08
- ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 8.0 8.1 8.2 8.3 8.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 12.0 12.1 Lua error in package.lua at line 80: module 'strict' not found.
| Periodic comets (by number) | ||
|---|---|---|
| Previous 132P/Helin–Roman–Alu |
7968 Elst–Pizarro | Next 134P/Kowal–Vávrová |
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