2001 QW322

2001 QW₃₂₂ is a trans-Neptunian object and binary system of the Kuiper belt, located in the outermost region of the Solar System. The cubewano was discovered at the Mauna Kea Observatories on 27 July 2001, by JJ Kavelaars, Jean-Marc Petit, Brett Gladman, and Matthew Holman. Later in 2001, Kavelaars discovered that it is a binary system. The diameter of the two components are estimated at 128 kilometers (80 miles) and 126 kilometers (78 miles).^[4]

Animation of CFHT images of the 2001 QW₃₂₂ pair, taken 30 minutes apart to show their motion relative to background stars and galaxies

Components of the 2001 QW₃₂₂ system resolved by the Hubble Space Telescope in 2017

2001 QW₃₂₂

2001 QW322 imaged by the Canada-France-Hawaii Telescope in 2001
Discovery[1]
Discovered by	John J. Kavelaars Jean-Marc Petit Brett J. Gladman Matthew J. Holman
Discovery site	Mauna Kea Obs.
Discovery date	27 July 2001
Designations
MPC designation	2001 QW322
Minor planet category	TNO cubewano[2][3][4]
Orbital characteristics[3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 4
Observation arc	18.11 yr (6,613 days)
Aphelion	44.306 AU (6.6281 Tm)
Perihelion	43.319 AU (6.4804 Tm)
Semi-major axis	45.294 AU (6.7759 Tm)
Eccentricity	0.02229
Orbital period (sidereal)	294.92 yr (107,720 d)
Mean anomaly	109.608°
Mean motion	0° 0m 12.031s / day
Inclination	4.7995°
Longitude of ascending node	124.635°
Argument of perihelion	92.373°
Known satellites	1 (D: 126 km; P: 6280 d)[1]
Physical characteristics
Mean diameter	128+2 −4 km (primary)[1] 126+3 −5 km (secondary)[1]
Mass	(2.150±0.184)×1018 kg[1]
Mean density	1±0.2 g/cm3[5]
Geometric albedo	0.093±0.008[1]
Absolute magnitude (H)	7.8[3]

In 2008, work was published showing that the binary has an extraordinarily long orbital period (for a binary trans-Neptunian object, asteroid or minor planet) of about 17 years.^[5] The orbital radius is also remarkably high (105,000 to 135,000 km) while the eccentricity is unusually low (< 0.4). All of these parameters are in the extremes of their normal ranges for such objects.^[5] The wide spacing and low eccentricity conspire to make the system prone to disruption, and its lifetime is estimated to be in the order of another billion years.^[5]