174567 Varda

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174567 Varda
Varda-ilmare hst.jpg
Hubble Space Telescope image of Varda and its satellite Ilmarë, taken in 2010
Discovery [1][2][3]
Discovered byJ. A. Larsen
Discovery siteKitt Peak National Obs.
Discovery date21 June 2003
Designations
MPC designation(174567) Varda
Pronunciation/ˈvɑːrdə/
Named after
Varda
(figure by J. R. R. Tolkien)[2]
2003 MW12
TNO[1] · cubewano[4]
detached[5] · distant[2]
Orbital characteristics[1]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 3
Observation arc36.39 yr (13,290 d)
Earliest precovery date19 March 1980
Aphelion52.505 AU
Perihelion39.589 AU
46.047 AU
Eccentricity0.1403
312.47 yr (114,129 d)
271.85°
0° 0m 11.52s / day
Inclination21.498°
183.98°
180.71°
Known satellitesIlmarë /ˈɪlmər/
D: 326 km; 361 km[6][7][8]
V−I = 1.266±0.052[7]
Physical characteristics
Mean diameter
716.6±4.8 km[9]
689 km[10]
705+81
−75
 km
[10][6]
722+82
−76
 km
[7]
Massapprox. 90%[11] of (2.664±0.064)×1020 kg[7]
Mean density
1.24+0.50
−0.35
 g/cm3
(system)[6][a]
0.015 g (at the poles)
0.012 g (at the equator)
5.61 h[7]
5.91 h[12]
Albedo0.102+0.024
−0.024
[6]
0.166+0.043
−0.033
[7]
Spectral type
B−V = 0.892±0.028
V−I = 1.133±0.034
B−V = 0.857±0.061
20.5[13]
3.097±0.060[7]
3.4[1]
3.61±0.05[6]

174567 Varda (Quenya: [ˈvarda]), provisional designation 2003 MW12, is a binary trans-Neptunian object of the resonant hot classical population of the Kuiper belt, located in the outermost region of the Solar System.[1] Its moon, named Ilmarë, was discovered in 2009.[8]

Brown estimates that, with an absolute magnitude of 3.5 and a calculated diameter of approximately 700 kilometers (430 miles), it is likely a dwarf planet.[10] However, Grundy et al. argue that objects such as Varda, 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.[14]

Discovery and orbit[edit]

Polar and ecliptic view of the orbit of Varda.

Varda was discovered in March 2006, using imagery dated from June 21, 2003 by Jeffrey A. Larsen with the Spacewatch telescope as part of a United States Naval Academy Trident Scholar project.[15]

It orbits the Sun at a distance of 39.6–52.5 AU once every 312 years and 6 months (114,129 days; semi-major axis of 46.05 AU). Its orbit has an eccentricity of 0.14 and an inclination of 21° with respect to the ecliptic.[1] The object is currently 47.5 AU from the Sun,[13] and will come to perihelion in November 2096.[5][16] It has been observed 68 times over 14 oppositions with precovery images back to 1980.[1]

Name[edit]

Names for Varda and its moon were announced on 16 January 2014. Varda is the queen of the Valar, creator of the stars, and principal goddess of the elves in J. R. R. Tolkien's fictional mythology. Ilmarë is a chief of the Maiar and Varda's handmaiden.[2]

Satellite[edit]

Varda has at least one satellite, Ilmarë /ˈɪlmər/ (stress on the first syllable, Quenya: [ˈilmarɛ]), or Varda I, which was discovered in an image obtained by the Hubble Space Telescope on 26 April 2009, and reported in 2011. It is estimated to be about 320–360 km in diameter (about 50% that of its primary). It constitutes approximately 8% of the system mass, or 2×1019 kg, assuming its density is the same as that of Varda.[11] As of 2015 two mirror orbital solutions are possible with slightly different parameters.[6][7]

Orbital parameters of the Varda–Ilmarë system [7]
Semi-major axis (km) Eccentricity Period (d) Inclination (°)
4809 ± 39 0.0215 ± 0.0080 5.75058 ± 0.00015 82–100

Physical properties[edit]

Based on its apparent brightness and assumed albedo, the estimated combined size of the Varda–Ilmarë system is 792+91
−84
 km
, with the size of the primary estimated at 705+81
−75
 km
. The total mass of the binary system is approximately 2.66×1020 kg. The density of both the primary and the satellite is estimated at about 1.24 g/cm3 assuming that they have equal density.[6][7]

On 10 September 2018, Varda's diameter was measured to be 716.6±4.8 km via stellar occultation.[9]

The surfaces of both the primary and the satellite appear to be red in the visible and near-infrared parts of the spectrum (spectral class IR), with Ilmarë being slightly redder than Varda. The spectrum of the system does not show water absorption but shows evidence of methanol ice. The rotation period of Varda is estimated at 5.61 hours.[7]

See also[edit]

Notes[edit]

  1. ^ This would be density of both Varda and Ilmarë if they have equal albedos and equal densities

References[edit]

  1. ^ a b c d e f g "JPL Small-Body Database Browser: 174567 Varda (2003 MW12)" (2016-08-07 last obs.). Jet Propulsion Laboratory. Retrieved 5 June 2018.
  2. ^ a b c d "174567 Varda (2003 MW12)". Minor Planet Center. Retrieved 5 June 2018.
  3. ^ "List Of Transneptunian Objects". Minor Planet Center. Retrieved 5 June 2018.
  4. ^ "MPEC 2009-P26 :Distant Minor Planets (2009 AUG. 17.0 TT)". Minor Planet Center. 7 August 2009. Retrieved 24 August 2009.
  5. ^ a b Marc W. Buie (15 April 2008). "Orbit Fit and Astrometric record for 174567". SwRI (Space Science Department). Retrieved 24 August 2009.
  6. ^ a b c d e f g Vilenius, E.; Kiss, C.; Mommert, M.; Müller, T.; Santos-Sanz, P.; Pal, A.; et al. (May 2012). ""TNOs are Cool": A survey of the trans-Neptunian region. VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects" (PDF). Astronomy and Astrophysics. 541: 17. arXiv:1204.0697. Bibcode:2012A&A...541A..94V. doi:10.1051/0004-6361/201118743. Retrieved 5 June 2018.
  7. ^ a b c d e f g h i j k Grundy, W. M.; Porter, S. B.; Benecchi, S. D.; Roe, H. G.; Noll, K. S.; Trujillo, C. A.; et al. (September 2015). "The mutual orbit, mass, and density of the large transneptunian binary system Varda and Ilmarë" (PDF). Icarus. 257: 130–138. arXiv:1505.00510. Bibcode:2015Icar..257..130G. doi:10.1016/j.icarus.2015.04.036. Retrieved 16 August 2017.
  8. ^ a b Johnston, Wm. Robert (31 January 2015). "Asteroids with Satellites Database – (450894) 2008 BT18". Johnston's Archive. Retrieved 5 June 2018.
  9. ^ a b "(174567) Varda 2018 Sep 10 716 ±4.8 x 716.6 km. PA 0.0°". Retrieved 15 April 2019.
  10. ^ a b c Brown, Michael E. "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 9 February 2018.
  11. ^ a b Using Grundy et al.'s working diameters of 361 km and 163 km, and assuming the densities of the two bodies are equal, Varda would contribute 91.6% of the system mass.
  12. ^ Thirouin, A.; Noll, K. S.; Ortiz, J. L.; Morales, N. (September 2014). "Rotational properties of the binary and non-binary populations in the trans-Neptunian belt". Astronomy and Astrophysics. 569: 20. arXiv:1407.1214. Bibcode:2014A&A...569A...3T. doi:10.1051/0004-6361/201423567. Retrieved 16 August 2017.
  13. ^ a b "AstDys (174567) 2003MW12 Ephemerides". Department of Mathematics, University of Pisa, Italy. Archived from the original on 18 April 2009. Retrieved 22 March 2009.
  14. ^ W.M. Grundy, K.S. Noll, M.W. Buie, S.D. Benecchi, D. Ragozzine & H.G. Roe, 'The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)', Icarus (forthcoming, available online 30 March 2019) DOI: 10.1016/j.icarus.2018.12.037,
  15. ^ Larsen, Jeffrey A.; Roe, Eric A.; Albert, C. Elise; et al. (2007). "The Search for Distant Objects in the Solar System Using Spacewatch". The Astronomical Journal. 133 (4): 1247–1270. Bibcode:2007AJ....133.1247L. doi:10.1086/511155.
  16. ^ "HORIZONS Web-Interface". JPL Solar System Dynamics. Retrieved 24 August 2009.

External links[edit]