(208996) 2003 AZ84

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(208996) 2003 AZ84
opposition)[12]
3.760±0.058 (V)[11]
3.537±0.053 (R)[13]

(208996) 2003 AZ84 (

provisional designation 2003 AZ84) is a trans-Neptunian object with a possible moon[6][9] located in 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][14] 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.[4]

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.[11][10]

It is considered a very likely dwarf planet by astronomers Gonzalo Tancredi and Michael Brown.[15][16] 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.[17]

Physical characteristics

The

Hershel data yielded a slightly higher estimate of 727.0+61.9
−66.5 km.[19] These results are in agreement with each other.[a]
The large size of 2003 AZ84 makes it a possible dwarf planet. However, if one assumes it to be in hydrostatic equilibrium, the density that results is too low for it to be solid, and hence it may not be a 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.[21] 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.[22]

In 2017, stellar occultations and data from its rotational lightcurve suggested that 2003 AZ84 had an elongated shape, presumably due to its rapid rotation rate of 6.71 hours, similar to Haumea and Varuna.[10] That would give 2003 AZ84 approximate dimensions of 940×766×490 km, with its longest axis nearly twice as long as its polar axis.

The spectra and colors of 2003 AZ84 are very similar to those of

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.[23]

Orbit and rotation

2003 AZ84 orbits the

perihelion (closest distance to the Sun) in 2107.[1] Simulations by the Deep Ecliptic Survey 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

U=2).[25] The shorter rotation period refers to the single-peaked solution, expected if the brightness variations resulted from albedo spots. The longer rotation period is for a double-peaked solution, more consistent with an elongated shape that is rotating edge-on.[26]

Polar view of 2003 AZ84's orbit (yellow) along with other plutinos.
Orbit of 2003 AZ84 (blue) compared to the orbits of Pluto and Neptune.

Satellite

S/2005 (208996) 1
Discovery
Discovered byBrown et al.
Discovery date2005
Orbital characteristics[8]
7200±300 km
12 d (prograde)
Satellite of2003 AZ84
Physical characteristics[8]
Mean radius
36±6 km

Using observations with the

arcsec and an apparent magnitude difference of 5.0.[6] As of 2012, attempts to recover the satellite have failed.[9] The unrecovered satellite is estimated to be about 72±12 km in diameter.[7][8]

Notes

  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.[20] 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.[19]

References

  1. ^ a b c d e f g "JPL Small-Body Database Browser: 208996 (2003 AZ84)" (2016-03-03 last obs.). Jet Propulsion Laboratory. Retrieved 9 February 2017.
  2. ^ Marsden, Brian G. (26 January 2003). "MPEC 2003-B27 : 2003 AZ84". Minor Planet Center. Retrieved 6 January 2010.
  3. ^
    Marc W. Buie (18 February 2009). "Orbit Fit and Astrometric record for 208996"
    . Southwest Research Institute. Retrieved 29 August 2009.
  4. ^ a b "208996 (2003 AZ84)". Minor Planet Center. Retrieved 9 February 2017.
  5. 3-sigma
    .)
  6. ^
    Bibcode:2007IAUC.8812....1B. Archived
    from the original on 19 July 2011.
  7. ^ a b c d e f Johnston, Wm. Robert (24 May 2019). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 6 July 2019.
  8. ^ a b c d e Johnston, Wm. Robert (20 September 2014). "(208996) 2003 AZ84". Johnston's Archive. Retrieved 16 January 2018.
  9. ^ a b c d Brown, Michael E. (3 February 2012). "After a bit more than 3 hrs on 2003AZ84 still no obvious moon". Twitter. Retrieved 3 February 2012.
  10. ^
    S2CID 119098862
    .
  11. ^
    S2CID 119489622
    .
  12. ^ a b "AstDys (208996) 2003AZ84 Ephemerides". Department of Mathematics, University of Pisa, Italy. Retrieved 6 July 2019.
  13. S2CID 55876118
    .
  14. ^ a b c Marsden, Brian G. (7 August 2009). "MPEC 2009-P26 : Distant Minor Planets (2009 August 17.0 TT)". Minor Planet Center. Retrieved 28 August 2009.
  15. doi:10.1017/S1743921310001717
    .
  16. ^ Brown, Michael E. (20 May 2019). "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 6 July 2019.
  17. S2CID 126574999, archived from the original
    (PDF) on 7 April 2019, retrieved 7 July 2019
  18. ISBN 978-0-8165-2755-7
    .
  19. ^
    S2CID 119253817
    .
  20. S2CID 118635387
    .
  21. Bibcode:2011epsc.conf.1060B
    .
  22. Bibcode:2011CBET.2675....1B
    .
  23. S2CID 118745903
    .
  24. ^ "Horizon Online Ephemeris System". Jet Propulsion Laboratory. Retrieved 6 July 2019.
  25. ^ "LCDB Data for (208996)". Asteroid Lightcurve Database (LCDB). Retrieved 9 February 2017.
  26. S2CID 189905992
    .
  27. ^ Parker, Joel Wm. (15 March 2007). "Distant EKOs #51". The Kuiper Belt Electronic Newsletter. Southwest Research Institute.

External links

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