28978 Ixion

28978 Ixion is a Kuiper belt object that was found on 22 May, 2001. Ixion is a plutino (an object that has a 2:3 orbital resonance with Neptune) and could be a dwarf planet. Astronomers think that it has a diameter of about 800 km, which makes it the third biggest plutino. It is named after Ixion, a figure from Greek mythology. Before it was named Ixion, it had the provisional designation 2001 KX₇₆.

28978 Ixion

Discovery
Discovered by	Deep Ecliptic Survey
Discovery date	22 May, 2001
Designations
MPC designation	28978 Ixion
Alternative names	2001 KX76
Minor planet category	TNO (plutino)[1]
Orbital characteristics[2]
Epoch 31 December, 2006 (JD 2 454 100.5)
Aphelion	7 370.503 Gm (49.269 AU)
Perihelion	4 501.495 Gm (30.091 AU)
Semi-major axis	5 935.999 Gm (39.680 AU)
Eccentricity	0.242
Orbital period	91 295.847 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	~650+260 −220 [3] < 822 km diameter[4]
Surface area	< 2.24×106 km²
Volume	< 3.15×108 km³
Mass	≈3×1020? kg[5]
Mean density	2.0? g/cm³
Surface gravity	< 0.229 7? m/s²
Escape velocity	< 0.434 6? km/s
Rotation period	? d
Albedo	0.15-0.37[4]
Temperature	≈44 K
Spectral type	(moderately red; B-V=1.03, V-R=0.61)
Apparent magnitude	19.6 (opposition)
Absolute magnitude (H)	3.2[2]