(208996) 2003 AZ84
(208996) 2003 AZ84 (provisional designation 2003 AZ84) is a trans-Neptunian object with a possible moon located in the outer regions of the Solar System. It is approximately 940 kilometers across its longest axis, as it has an elongated shape. It belongs to the plutinos – a group of minor planets named after its largest member Pluto – as it orbits in a 2:3 resonance with Neptune in the Kuiper belt. It is the third-largest known plutino, after Pluto and Orcus. It was discovered on 13 January 2003, by American astronomers Chad Trujillo and Michael Brown during the NEAT survey using the Samuel Oschin telescope at Palomar Observatory.
2003 AZ84 and its possible satellite, imaged by the Hubble Space Telescope on 2 December 2005. | |
| Discovery | |
|---|---|
| Discovered by | C. Trujillo M. E. Brown |
| Discovery site | NEAT–Palomar Obs. |
| Discovery date | 13 January 2003 |
| Designations | |
MPC designation | 2003 AZ84 |
Minor planet category | TNO · plutino · distant |
| Orbital characteristics | |
| Epoch 27 April 2019 (JD 2458600.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 20.96 yr (7,654 days) |
| Earliest precovery date | 19 March 1996 |
| Aphelion | 46.555 AU |
| Perihelion | 32.170 AU |
Semi-major axis | 39.362 AU |
| Eccentricity | 0.183 |
Orbital period (sidereal) | 246.96 yr (90,202 days) |
Mean anomaly | 232.611° |
Mean motion | 0° 0m 14.368s / day |
| Inclination | 13.596° |
Longitude of ascending node | 252.202° |
| ≈ 27 March 2107 ±2.2 days | |
| 15.211° | |
| Known satellites | 1 (diameter: 72 km) (unrecovered) |
| Physical characteristics | |
| Dimensions | ? (940±40)×(766±20)×(490±16) km (derived from assumption of hydrostatic equilibrium) |
Mean diameter | ? 772±12 km (assuming HE) 723 km (for albedo 0.097) |
| Mass | ? 210×1018 kg (derived from ) 150×1018 kg (derived from ) |
Mean density | ? 0.87±0.01 g/cm3 (assuming HE) 0.76 g/cm3 |
Synodic rotation period | 6.7874±0.0002 h |
| ? 0.097±0.009 (assuming HE) 0.097 | |
| 20.3 (opposition) | |
| 3.760±0.058 (V) 3.537±0.053 (R) | |
Though elongated in shape, 2003 AZ84 displays a small lightcurve amplitude due to its rotation axis being oriented nearly pole-on; the variability is mainly caused by albedo features on its surface.
It is considered a very likely dwarf planet by astronomers Gonzalo Tancredi and Michael Brown. However, Will M. Grundy et al. conclude that objects such as this, in the size range of 400–1,000 km, with albedos less than ≈0.2 and densities of ≈1.2 g/cm3 or less, have likely never compressed into fully solid bodies, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets.