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(208996) 2003 AZ84

From Wikipedia, the free encyclopedia

(208996) 2003 AZ84
2003AZ84 Hubble.png
2003 AZ84 and its possible satellite, imaged by the Hubble Space Telescope on 2 December 2005.
Discovery [1][2]
Discovered byC. Trujillo
M. E. Brown
Discovery siteNEATPalomar Obs.
Discovery date13 January 2003
MPC designation(208996) 2003 AZ84
2003 AZ84
TNO[1] · plutino[3][4][5] · distant[6]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 3
Observation arc20.96 yr (7,654 days)
Earliest precovery date19 March 1996
Aphelion46.627 AU
Perihelion32.392 AU
39.510 AU
248.35 yr (90,710 days)
0° 0m 14.4s / day
Known satellites1[7] (diameter: 72 km)[4][8]
Physical characteristics
Dimensions940 × 766 × 490 km[10]
Mean diameter
573±21 km (or larger)[11]
686±96 km[12]
727±67 km[13]
723±64 km (derived)[8]
737.06 km (derived)[14]
747 km[15]
772 km[4]
6.71±0.05 h[16]
6.76±0.02 h[17]
6.79±0.05 h[18]
13.42 h[14]
0.10 (assumed)[14]
0.11 (radiometric)[15]
BB [19][20] · C[14]
B–V = 0.67±0.05[13]
V–R = 0.38±0.04[13]
20.2 (opposition)[21]
3.54±0.03(V), 3.08±0.03(R)[23]

(208996) 2003 AZ84 is a trans-Neptunian object with a possible moon[7][9] from the outer regions of the Solar System. It is approximately 940 kilometers across its longest axis, as it has an elongated shape.[10] 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.[3][5] 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.[6]

Its lightcurve amplitude deviates little from that of a Jacobi ellipsoid, which suggests that it is likely one with small albedo spots.[26]

Considered a very likely dwarf planet by astronomers Gonzalo Tancredi and Michael Brown, it is currently not recognized as such by the IAU.[27][15] Objects such as this, in the size range of 400–1000 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, and so are highly unlikely to be dwarf planets.[28]

Orbit and rotation

Orbit of 2003 AZ84 (blue) compared to the orbits of Pluto and Neptune
Orbit of 2003 AZ84 (blue) compared to the orbits of Pluto and Neptune

2003 AZ84 is a plutino, which means that it is in a 2:3 orbital resonance with Neptune, similar to that of Pluto.[5] It orbits the Sun in just over 247 Earth years. It is currently 45.3 AU from the Sun[21] and came to aphelion (farthest distance from the Sun) in 1982.[29] 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]

Two rotational lightcurves of this minor planet were obtained by Scott Sheppard and José Ortiz in 2003 and 2006. Lightcurve analysis gave an ambiguous rotation period of 6.71 and 6.76 hours with a brightness variation of 0.14 and 0.10 in magnitude, respectively (U=2/2-).[16][17]

Physical characteristics

The Spitzer Space Telescope has estimated its size at 686±96 km,[12] while an analysis of a combination of Spitzer and Hershel data yielded a slightly higher estimate of 727.0+61.9
.[13] These results are in agreement with each other.[note 1] Its large size of 2003 AZ84 makes it a probable dwarf planet. Its mass is unknown since the satellite has not been recovered.[9]

A stellar occultation in 2010 measured a single chord of 573±21 km.[31] But this is only a lower limit for the diameter of 2003 AZ84 because the chord may not have passed through the center of the body.

Later in 2017, stellar occultations and data from its rotational lightcurve have suggested that 2003 AZ84 has an elongated shape from its rapid rotation of at least 6.71 hours, similarly to Haumea and Varuna.[10] This gives 2003 AZ84 approximate dimensions of 940 × 766 × 490 km, with its longest axis nearly twice as large as its polar axis.

The spectra and colors of 2003 AZ84 are very similar to those of Orcus, another large object in 2:3 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.[32]


Using observations with the Hubble Space Telescope, the discovery of a satellite of 2003 AZ84 was reported in IAUC 8812 on 22 February 2007.[8][7][33] The object was measured with a separation of 0.22 arcsec and an apparent magnitude difference of 5.0.[7] As of 2012, attempts to recover the satellite have failed.[9] The unrecovered satellite is estimated to be about 72±12 km in diameter.[4][8]


  1. ^ The results of the previous observation of (208996) 2003 AZ84 by the Herschel were reported in 2010. They were obtained using chop/nod technique yielding 910±60 km.[30] The difference can be explained by the large light-curve amplitude of (208996) 2003 AZ84 and the fact that in 2010 the radiation from it was measured at one particular time, while 2012 determination was based on the time-averaged data.[13]


  1. ^ a b c d "JPL Small-Body Database Browser: 208996 (2003 AZ84)" (2016-03-03 last obs.). Jet Propulsion Laboratory. Retrieved 9 February 2017.
  2. ^ Marsden, Brian G. (2003-01-26). "MPEC 2003-B27 : 2003 AZ84". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 2010-01-06.
  3. ^ a b c Marc W. Buie (2009-02-18). "Orbit Fit and Astrometric record for 208996". SwRI (Space Science Department). Retrieved 2009-08-29.
  4. ^ a b c d e Johnston, Wm. Robert (30 December 2017). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 16 January 2018.
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  6. ^ a b "208996 (2003 AZ84)". Minor Planet Center. Retrieved 9 February 2017.
  7. ^ a b c d Brown, M. E.; Suer, T.-A. (February 2007). "Satellites of 2003 AZ_84, (50000), (55637), and (90482)". IAU Circ. (8812). Bibcode:2007IAUC.8812....1B. Retrieved 9 February 2017.
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  9. ^ a b c d Plutokiller (2012-02-03). "After a bit more than 3 hrs on 2003AZ84 still no obvious moon". Twitter. Retrieved 2012-02-03.
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External links

This page was last edited on 26 May 2019, at 20:13
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