| Discovered by | C. Trujillo, M. Brown, (644) |
|---|---|
| Discovery date | January 13, 2003 |
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Designations
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| MPC designation | (208996) 2003 AZ84 |
| Alternate name(s) | none |
| Minor planet category |
Plutino[3][4] |
| Epoch July 23, 2010 (JD 2455400.5) | |
| Aphelion | 46.477 AU (6.9529 Tm) |
| Perihelion | 32.334 AU (4.8371 Tm) |
| Semi-major axis | 39.406 AU (5.8950 Tm) |
| Eccentricity | 0.179 |
| Orbital period | 247.37 a (90,352 d) |
| Mean anomaly | 218.919° |
| Inclination | 13.563° |
| Longitude of ascending node | 252.016° |
| Argument of perihelion | 15.874° |
| Satellites | 1 (68 km)[5] |
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Physical characteristics
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| Dimensions | 686 ± 96 km[6] 910 ± 60 km[7] > 573 ± 21 km[8] |
| Surface area | ~2×106 km2 |
| Volume | ~2.7×108 km³ |
| Mass | ~5.3×1020 kg |
| Mean density | 2.0 g/cm³ (assumed) |
| Equatorial surface gravity | ~0.21 m/s² |
| Escape velocity | ~0.41 km/s |
| Sidereal rotation period |
13.44 hr[1] |
| Albedo | 0.09–0.16[6] 0.07 ± 0.02[7] |
| Temperature | ~44 K |
| Spectral type | B-V=0.70; V-R=0.36[9] |
| Apparent magnitude | 20.2 (opposition)[10] |
| Absolute magnitude (H) | 4.00 (JPL)[1][2] 3.83 (Herschel)[7][9] 3.71 (Spitzer)[6] 3.65[3] |
(208996) 2003 AZ84, also written as 2003 AZ84, is a plutino, like Pluto, in a 2:3 resonance with Neptune.[3][4] It is very likely a dwarf planet. It was discovered on January 13, 2003 by C. Trujillo and M. Brown[1] using the Samuel Oschin telescope in the Palomar Observatory. Light-curve-amplitude analysis shows only small deviations, suggesting that 2003 AZ84 is a spheroid with small albedo spots and hence a dwarf planet.[11]
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It is classified as a plutino, which means that it is in a 3:2 orbital resonance with Neptune, similar to that of Pluto.[4] It orbits the Sun in just over 247 Earth years.
2003 AZ84 is currently 45.3 AU from the Sun[10] and came to aphelion (farthest distance from the Sun) in 1982.[12] It will come to perihelion in 2107.[1] Simulations by the Deep Ecliptic Survey (DES) show that over the next 10 million years 2003 AZ84 will not come closer (qmin) than 31.6 AU from the Sun (it will stay farther away than Neptune).[3]
The rotation period of 2003 AZ84 is not exactly known, but the most likely value is about 6.7 hours.[13]
The Spitzer Space Telescope has estimated it to have a size of 686 ± 96 km,[6] while an analysis of a combination of Spitzer and Hershel data yielded a somewhat higher estimate of 910 ± 60 km.[7] Due to its large size 2003 AZ84 qualifies as a plutoid candidate. Its mass is unknown, but a reasonable estimate is 3–5×1020 kg.
The spectra and colors of 2003 AZ84 are very similar to those of Orcus, another large planetoid in 3:2 resonance with Neptune. Both bodies have a flat featureless spectrum in the visible and moderately strong water ice absorption bands in the near-infrared, although 2003 AZ84 has a lower albedo. Both bodies also have a weak absorption band near 2.3 μm, which may be caused by ammonia hydrate or methane ice.[14]
A stellar occultation in 2010 measured a single chord of 573±21 km.[8] But this is only a lower limit for the diameter of 2003 AZ84 as the chord may not have passed through the center of the body.
The discovery of a satellite of 2003 AZ84 was reported in IAUC 8812 on 22 February 2007.[5][15] The orbit of this satellite has yet to be determined, but was measured with a separation of 0.22 arcsec and an apparent magnitude difference of 5.0. It is estimated to be about 68 ± 20 km in diameter.[5]
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