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7968 Elst–Pizarro

Astronomical object in the Solar System

Field	Value
minorplanet	yes
background	#D6D6D6
name	7968 Elst–Pizarro
133P/Elst–Pizarro
image	7968 Elst–Pizarro Eso9637ainvert.jpg
caption
discoverer	:
M. R. S. Hawkins
R. H. McNaught, S. J. Bus
Eric W. Elst, Guido Pizarro
discovered	24 July 1979 ()
14 July 1996 (1996 N2)
mpc_name	(7968) Elst–Pizarro
alt_names	P/1996 N2

mp_category	Main-belt comet
Main-belt asteroid
Themis/ Beagle family
orbit_ref
epoch	13 January 2016 (JD 2457400.5)
semimajor	3.1600 AU (a)
perihelion	2.6524 AU (q)
time_periastron	2024-May-10{{cite web
title	Horizons Batch for 7968 Elst-Pizarro (1996 N2) on 2024-May-10
publisher	JPL Horizons
type	Perihelion occurs when rdot flips from negative to positive
url	https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27133P%27&START_TIME=%272024-May-10%27&STOP_TIME=%272024-May-11%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2719%27
accessdate	2023-04-29}} (JPL#70/Soln.date: 2023-Apr-25
aphelion	3.66751 AU (Q)
eccentricity	0.16062 (e)
period	5.62 yr (2051.7 d)
inclination	1.3873° (i)
asc_node	160.14° (Ω)
arg_peri	131.97° (ω)
mean_anomaly	187.70° (M)
avg_speed	16.64 km/s
dimensions	3.8 +/-
km
density	1.3 g/cm3
rotation	3.471 h
magnitude	17.24 to 20.71
abs_magnitude	15.7
15.3R (2004)
15.49R (2010)
albedo	0.074±0.013R
single_temperature	160 K
mean_motion	/ day (n)
observation_arc	13350 days (36.55 yr)
uncertainty	0
jupiter_moid	1.51427 AU
tisserand	3.185

133P/Elst–Pizarro M. R. S. Hawkins R. H. McNaught, S. J. Bus : Eric W. Elst, Guido Pizarro 14 July 1996 (1996 N2)

Main-belt asteroid Themis/ Beagle family km 15.3R (2004) 15.49R (2010)

Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets, and is the prototype of active asteroids. 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.

Subsequently, around the next perihelion in November 2001, the cometary activity appeared again, and persisted for 5 months. It again came to perihelion on 8 February 2013. The outgassing was found to happen only on small part of the surface measuring less than 600 m in effective diameter, likely being the relatively recent (younger than 100 million years) impact crater.

At present, seven 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), 118401 LINEAR (176P/LINEAR), (282P/2003 BM80), (288P/2006 VW139), (362P/2008 GO98), and (433P/2005 QN173). As a dual status object, astrometric observations of 7968 Elst–Pizarro should be reported under the minor planet designation.

Exploration

Castalia is a proposed mission concept for a robotic spacecraft to explore Elst–Pizarro and make the first in situ measurements of water in the asteroid belt, and thus, help solve the mystery of the origin of Earth's water. The lead is Colin Snodgrass, from The Open University in the UK. Castalia was proposed in 2015 and 2016 to the European Space Agency within the Cosmic Vision programme missions M4 and M5, but it was not selected. The team continues to mature the mission concept and science objectives. Because of the construction time required and orbital dynamics, a launch date of October 2028 was proposed.

Castalia mission scientists are now considering instrument contributions for the Chinese ZhengHe comet exploration mission, which will conduct detailed remote sensing and in-situ measurements at Elst–Pizarro in 2032 following a proposed launch in 2025.

References

|archive-url=https://web.archive.org/web/20110806021852/http://www.ifa.hawaii.edu/~hsieh/mbcs.shtml |url-status=dead |archive-date=2011-08-06 |access-date=2010-12-15

|author-link=David C. Jewitt |access-date=2010-12-15}}

|access-date=13 April 2016 |url-status=dead |archive-url=https://archive.today/20120809003324/http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=133P |archive-date=9 August 2012

|doi-access=free

|access-date=2018-02-13}}

References

(2020). "Active Asteroids". Oxford University Press.
(16 September 1996). "Strange Comet Discovered at ESO". ESO.
[https://minorplanetcenter.net/iau/ECS/MPCArchive/2021/MPC_20210920.pdf M.P.C. 133823]
(2018). "The Castalia mission to Main Belt Comet 133P/Elst-Pizarro". Advances in Space Research.
Snodgrass, Colin. (October 2018). "Exploring the next frontier: the Main Belt Comets – Chinese MBC mission". [[University of Edinburgh]].
Jones, Andrew. (30 June 2021). "China outlines space plans to 2025". [[SpaceNews]].

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