28978 Ixion

Infobox Planet


discovery=yes
physical_characteristics = yes
bgcolour=#FFFFC0
name=28978 Ixion
discoverer = Deep Ecliptic Survey
discovered = 22 May, 2001
mp_name = 28978 Ixion
alt_names=mp|2001 KX|76
mp_category = TNO (plutino)cite web
author=Marc W. Buie
date=2007/07/12
title=Orbit Fit and Astrometric record for 28978
publisher=SwRI (Space Science Department)
url=http://www.boulder.swri.edu/~buie/kbo/astrom/28978.html
accessdate=2008-09-29]
orbit_ref =cite web
date=2007-07-12 last obs
title=JPL Small-Body Database Browser: 28978 Ixion (2001 KX76)
url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Ixion
accessdate=2008-10-04]
epoch=December 31, 2006 (JD 2 454 100.5)
semimajor=5 935.999 Gm (39.680 AU)
perihelion=4 501.495 Gm (30.091 AU)
aphelion=7 370.503 Gm (49.269 AU)
eccentricity=0.242
period=91 295.847 d (249.95 a)
inclination=19.584°
asc_node=71.028°
arg_peri=298.779°
mean_anomaly=268.546°
avg_speed=4.66 km/s
dimensions=< 822 km diametercite web|url=http://www.johnstonsarchive.net/astro/tnodiam.html |title=TNO/Centaur diameters and albedos|author=Wm. Robert Johnston ]
surface_area=< 2.24e|6 km²
volume=< 3.15e|8 km³
mass=< 5.8e|20? kg
density=2.0? g/cm³
surface_grav=< 0.229 7? m/s²
escape_velocity=< 0.434 6? km/s
rotation=? d
spectral_type =(moderately red; B-V=1.03, V-R=0.61)
magnitude = 19.6 (opposition)
abs_magnitude=3.2
albedo=0.15-0.37
single_temperature=~44 K

28978 Ixion (pronEng|ɪkˈsaɪən, "," sometimes erroneously IPA|/ˈɪksiən/, "IK-see-ən," from _la. Ixīōn , _gr. "Ιξίων)" is a Kuiper belt object discovered on May 22, 2001. Ixion is a plutino (an object that has a 2:3 orbital resonance with Neptune); its estimated diameter of 800 km makes it the third largest plutino. It is named after Ixion, a figure from Greek mythology; it previously had the provisional designation mp|2001 KX|76.

Physical characteristics

Ixion is moderately red (slightly redder than 50000 Quaoar) and it has a higher albedo (0.15) than the mid-sized red cubewanos.

The latest spectroscopic results indicate that Ixion's surface is a mixture of dark carbon and tholin, which is a heteropolymer formed by irradiation of clathrates of water and organic compounds (see TNO spectra). Water ice absorption lines (1.5 and 2μm) were absent (Licandro "et al." 2002). Unlike Varuna, Ixion does not show greater reflectivity for longer waves (the so-called red slope) in infrared.

Other than Pluto, Ixion was the first TNO discovered that was originally estimated to be larger than asteroid Ceres.cite web
date=2001-08-24
title=New object deemed largest minor planet
publisher=CNN (space)
author=Richard Stenger
url=http://edition.cnn.com/2001/TECH/space/08/24/minor.planet/index.html
accessdate=2008-02-29] But more recent estimates suggest that Ixion has a high albedo and is smaller than Ceres. It is more likely that 20000 Varuna or 50000 Quaoar may turn out to the first TNO discovered that is larger than Ceres.

The Very Large Telescope (VLT) has checked Ixion for cometary activity, but did not detect a coma.cite journal
author=O. Lorin and P. Rousselot
title=Search for cometary activity in three Centaurs (60558) Echeclus, 2000 FZ53 and 2000 GM137 and two trans-Neptunian objects (29981) 1999 TD10 and (28978) Ixion
journal=Royal Astronomical Society
volume=376 |issue=2 |pages=881–889 |year=2007
doi=10.1111/j.1365-2966.2007.11487.x
url=http://www3.interscience.wiley.com/journal/117974948/abstract
accessdate=2008-10-04 ]

Orbit

Ixion and Pluto follow similar but differently oriented orbits: Ixion’s perihelion is below the ecliptic whereas Pluto's is above it. Uncharacteristically for bodies locked in resonance with Neptune (such as Orcus), Ixion approaches Pluto with less than 20 degrees of angular separation. Ixion is currently crossing the ecliptic heading below, and will reach its perihelion in 2070. Pluto has passed its perihelion (1989) and is descending toward the ecliptic. Ixion's orbital period is almost 250 Earth years, about 0.5% larger than Pluto's.

ee also

* Comparison of colours of trans-Neptunian objects

References

*cite journal | author= H. Boehnhardt, S. Bagnulo, K. Muinonen, M. A. Barucci, L. Kolokolova, E. Dotto and G. P. Tozzi|title=Surface characterization of 28978 Ixion (mp|2001 KX|76)| journal=Astronomy & Astrophysics | volume=415| year=2003 | pages=L17–L19 [http://www.astro.helsinki.fi/~psr/Papers/Ixion-AAL.pdf Pre-print] about Ixion's surface from the Planetary Systems Research group of the University of Helsinki

*cite journal | author=J. Licandro, F. Ghinassi, L. Testi| title="Infrared spectroscopy of the largest known trans-neptunian object mp|2001 KX|76"| journal=Astronomy & Astrophysics | year=2002 | volume=388 | pages=L9 | doi=10.1051/0004-6361:20020533 [http://arxiv.org/abs/astro-ph/0204104 Pre-print on arXiv]

*cite journal | author=W. J. Altenhoff, F. Bertoldi and K. M. Menten| title="Size estimates of some optically bright KBOs"| journal=Astronomy & Astrophysics | volume=415| year=2004

External links

* [http://hamilton.dm.unipi.it/cgi-bin/astdys/astibo?objects:Ixion;main AstDys] orbital elements
* [http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Ixion;orb=1;view=Far Orbital simulation] from JPL (Java) / [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=Ixion Ephemeris]