|
Discovery
|
|
|---|---|
| Discovered by | M. R. S. Hawkins and R. H. McNaught[1] and/or S. J. Bus [2] (as 1979 OW7) as well as Eric W. Elst and Guido Pizarro (as 1996 N2) |
| Discovery date | 24 July 1979 (as 1979 OW7) [3] and 14 July 1996 (as 1996 N2) |
|
Designations
|
|
| Alternate name(s) | P/1996 N2, 1979 OW7 |
| Minor planet category |
Main-belt comet[4][5] Main-belt asteroid[6] Themis/Beagle family[4] |
| Epoch 23 July 2010 (JD 2455400.5) T_jup = 3.184 |
|
| Aphelion | 3.6729 AU (Q) (549.45 Gm) |
| Perihelion | 2.6462 AU (q) (395.86 Gm) |
| Semi-major axis | 3.1596 AU (a) (472.66 Gm) |
| Eccentricity | 0.16246 |
| Orbital period | 5.62 yr (2051.3 d) |
| Average orbital speed | 16.64 km/s |
| Mean anomaly | 196.46° |
| Inclination | 1.3863° |
| Longitude of ascending node | 160.15° |
| Argument of perihelion | 132.29° |
|
Physical characteristics
|
|
| Dimensions | 3.8±0.6 km (Spitzer)[7] |
| Mean density | 1.3(?) g/cm³[8] |
| Rotation period | 3.471 hr (0.1446 d)[6] |
| Albedo | 0.05±0.02R[7] |
| Temperature | 160K[8] |
| Apparent magnitude | 17.24 to 20.71 |
| Absolute magnitude (H) | 14.0[6] 15.3R (2004)[8] 15.49R (2010)[9] |
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.
Elst–Pizarro was reported in 1979 as minor planet 1979 OW7, with its image on a photographic plate being completely stellar in appearance. The 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 on 1996 August 7 when a linear dust feature was observed.[8]
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).[11] As a dual status object, astrometric observations of 7968 Elst–Pizarro should be reported under the minor planet designation.[11]
It will come to perihelion on 8 February 2013.[6]
|
|||||
| Periodic comets (by number) | ||
|---|---|---|
| Previous 132P/Helin-Roman-Alu |
7968 Elst–Pizarro | Next 134P/Kowal-Vávrová |
|
||||||||||||||||||||||