28978 Ixion

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**28978 Ixion**
Discovery
Image:Ixion planetoid nasa.jpg
Discovered by	Deep Ecliptic Survey
Discovery date	22 May, 2001
Designations
MPC designation	28978 Ixion
Alternative names	2001 KX₇₆
Minor planet category	TNO (plutino)
Orbital characteristics
Epoch December 31, 2006 (JD 2454100.5)
Aphelion	7370.503 Gm (49.269 AU)
Perihelion	4501.495 Gm (30.091 AU)
Semi-major axis	5935.999 G m (39.680 AU)
Eccentricity	0.242
Orbital period	91295.847 d (249.95 a)
Average orbital speed	4.66 km/s
Mean anomaly	268.546°
Inclination	19.584°
Longitude of ascending node	71.028°
Argument of perihelion	298.779°
Physical characteristics
Dimensions	<822 km diameter^[2]
Surface area	<2.24×10⁶ km²
Volume	<3.15×10⁸ km³
Mass	<5.8×10²⁰? kg
Mean density	2.0? g/cm³
Equatorial surface gravity	<0.2297? m/s²
Escape velocity	<0.4346? km/s
Rotation period	? d
Albedo	0.15-0.37^[2]
Temperature	~44 K
Spectral type	(moderately red; B-V=1.03, V-R=0.61)
Apparent magnitude	19.6
Absolute magnitude	3.244

28978 Ixion (pronounced /ɪkˈsaɪən/, ik-sye'-ən, sometimes /ˈɪksiən/, ik'-see-ən; from Latin: Ixīōn, Greek: 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 2001 KX₇₆.

1 Physical characteristics
2 Orbit
3 See also
4 References
5 External links

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 absobtion 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.^[3] But more recent estimates suggest that Ixion has a high albedo^[2] 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.

Orbit

Image:TheKuiperBelt Orbits Ixion2.svg

This diagram shows the orbits of Ixion (green), Pluto (red) and Neptune (grey). The current positions of Ixion and Pluto are indicated (as of April 2006).

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.

References

^ [1]
^ ^a ^b ^c Wm. Robert Johnston. TNO/Centaur diameters and albedos.
^ Richard Stenger (August 24, 2001). New object deemed largest minor planet. CNN (space). Retrieved on 2008-02-29.

H. Boehnhardt, S. Bagnulo, K. Muinonen, M. A. Barucci, L. Kolokolova, E. Dotto and G. P. Tozzi (2003). "Surface characterization of 28978 Ixion (2001 KX₇₆)". Astronomy & Astrophysics 415: L17-L19. Pre-print about Ixion's surface from the Planetary Systems Research group of the University of Helsinki

J. Licandro, F. Ghinassi, L. Testi (2002). "Infrared spectroscopy of the largest known trans-neptunian object 2001 KX₇₆". Astronomy & Astrophysics. Pre-print on arXiv

W. J. Altenhoff, F. Bertoldi and K. M. Menten (2004). "Size estimates of some optically bright KBOs". Astronomy & Astrophysics 415.

External links

AstDys orbital elements
Orbital simulation from JPL (Java) / Ephemeris

v • d • e Minor planets navigator
(28977) 2001 KP73 \| 28978 Ixion \| (28979) 2001 LW

v • d • e Trans-Neptunian objects
Pronunciation guide Objects in italics are unnnumbered.
Plutinos	Pluto¹ · 1993 SB · 1993 SC · 1994 JR₁ · 1994 TB · 1995 QZ₉ · 1996 SZ₄ · 1996 TP₆₆ · 1996 TQ₆₆ · 1997 QJ₄ · 1998 HK₁₅₁ · 1998 US₄₃ · 1998 VG₄₄ · 1998 WW₂₄ · 1998 WU₃₁ · 38083 Rhadamanthus · 1999 TC₃₆ · 38628 Huya · 28978 Ixion · 2002 KX₁₄ · 2002 VR₁₂₈ · 2003 VS₂ · 90482 Orcus · 1993 RO · 1993 RP · 2003 AZ₈₄ · 2001 QF₂₉₈
Cubewanos	1992 QB₁ · 1994 GV₉ · 1994 JQ₁ · 1994 VK₈ · 1995 GJ · 1995 SM₅₅ · 1996 TO₆₆ · 58534 Logos · 1997 CS₂₉ · 1997 CU₂₉ · 1998 HJ₁₅₁ · 1998 HP₁₅₁ · 1998 HM₁₅₁ · 1998 KR₆₅ · 19521 Chaos · 1998 WA₂₅ · 1999 DF₉ · 1999 HT₁₁ · 53311 Deucalion · 20000 Varuna · 2002 AW₁₉₇ · 50000 Quaoar · 2002 TX₃₀₀ · 2002 UX₂₅ · 2003 EL₆₁ · 2003 OP₃₂ · 2004 GV₉ · 2005 FY₉ · 2005 RN₄₃ · 88611 Teharonhiawako · 1998 WW₃₁ · 2002 MS₄ · 2003 MW₁₂ · 2003 QW₉₀
Twotinos	1996 TR₆₆ · 1998 SM₁₆₅ · 1999 RB₂₁₆ · 2000 JG₈₁ · 2002 WC₁₉ · 1997 SZ₁₀
Other resonant objects	1994 JS · 1995 DA₂ · 1998 WA₃₁ · 1999 CP₁₃₃ · 1999 DE₉ · 1999 HB₁₂ · 2001 KC₇₇ · 2001 KP₇₇ · 2002 TC₃₀₂ · 2003 LG₇
Scattered disc objects	Eris^{1, 2} · 1995 TL₈ · 1996 GQ₂₁ · 1996 TL₆₆ · 1999 CC₁₅₈ · 2000 EE₁₇₃ · 2000 OO₆₇ · 2000 OM₆₇ · 2001 UR₁₆₃ · 2002 CY₂₂₄ · 2002 GX₃₂ · 2002 RP₁₂₀ · 90377 Sedna² · 2005 RM₄₃ · 2000 CR₁₀₅ 2004 XR₁₉₀ · 2005 TN₇₄ · 2006 QH₁₈₁
Unclassified	1997 CR₂₉ · 1998 SN₁₆₅ · 1999 CL₁₅₈ · 1999 HC₁₂ · 1999 KR₁₆ · 1999 OY₃ · 2003 FY₁₂₈ · 2004 SB₆₀ · 2004 TY₃₆₄ · 2005 RR₄₃
Natural satellites	Charon (Pluto) · Hydra (Pluto) · Nix (Pluto) · Dysnomia (Eris) · S/2000 (1998 WW₃₁) 1 · S/2005 (2003 EL₆₁) 1 · S/2005 (2003 EL₆₁) 2 · Zoe (Logos) · S/2005 (79360) 1 · Sawiskera (Teharonhiawako)
¹ Also classified as a dwarf planet. ² Although currently classified as an SDO, Eris and Sedna may be part of the inner Oort Cloud.

v • d • e trans-Neptunian dwarf planets and candidates
Kuiper belt:	Orcus · Pluto · Ixion · 2002 UX₂₅ · Varuna · 2002 TX₃₀₀ · 2003 EL₆₁ · Quaoar · 2005 FY₉ · 2002 AW₁₉₇
Scattered disc:	2002 TC₃₀₂ · Eris · 2004 XR₁₉₀ · Sedna
See also Triton, astronomical objects and the solar system's list of objects, sorted by radius or mass. For pronunciation, see: Centaur and TNO pronunciation.

v • d • e Small Solar System bodies
Vulcanoids · Near-Earth asteroids · Main belt · Jupiter Trojans · Centaurs · Damocloids · Neptune Trojans · Comets Trans-Neptunians (Kuiper belt · Scattered disc objects · Oort cloud)
For other objects and regions, see Asteroid groups and families, Binary asteroids, Asteroid moons, meteoroids and the Solar System. For a complete listing, see List of minor planets. See also Pronunciation of asteroid names and Meanings of asteroid names.