Astronomy:174567 Varda

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Short description: Trans-Neptunian object
174567 Varda Varda symbol (bold).svg (astrological)
Varda.gif
Hubble Space Telescope image of Varda and its satellite Ilmarë, taken in 2010 and 2011
Discovery[1][2][3]
Discovered byJ. A. Larsen
Discovery siteKitt Peak National Obs.
Discovery date21 June 2003
Designations
Designation
(174567) Varda
Pronunciation/ˈvɑːrdə/
Named afterVarda
(figure by J. R. R. Tolkien)[2]
2003 MW12
Minor planet categoryTNO[1] · cubewano[4]
detached[5] · distant[2]
Orbital characteristics[1]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 2
Observation arc39.12 yr (14,290 d)
Earliest precovery date19 March 1980
|{{{apsis}}}|helion}}52.711 AU
|{{{apsis}}}|helion}}39.510 AU
46.110 AU
Eccentricity0.14315
Orbital period313.12 yr (114,366 d)
Mean anomaly275.208°
Mean motion0° 0m 11.332s / day
Inclination21.511°
Longitude of ascending node184.151°
|{{{apsis}}}|helion}}≈ 1 November 2096[6]
±4 days
180.072°
Known satellites1 (Ilmarë)
Physical characteristics
Mean diameter740±14 km (area equivalent)[7]
722+82
−76 km[lower-alpha 1][8]
Flattening0.080±0.049 (for period of 11.82 h)[7]
or 0.235±0.050 (for period of 5.91 h)[7]
Mass(2.45±0.06)×1020 kg[7][lower-alpha 2]
Mean density1.23±0.04 g/cm3 (for period of 11.82 h)[7]
1.78±0.06 g/cm3 (for period of 5.61 h)[7]
Rotation period5.61 h[8] or 5.91 h (single-peaked)[9]
11.82 h (double-peaked)[9]
Albedo0.099±0.002 (primary)[7]
0.102+0.024
−0.024[10]
Spectral type
IR (moderately red)[8]
B−V=0.886±0.025[8]
V–R=0.55±0.02[11]
V−I=1.156±0.029[8]
Apparent magnitude20.5[12]
Absolute magnitude (H)3.81±0.01 (primary)[7]
3.097±0.060[8]
3.4[1]


174567 Varda (provisional designation 2003 MW12) is a binary trans-Neptunian planetoid of the resonant hot classical population of the Kuiper belt, located in the outermost region of the Solar System.[1] Its moon, Ilmarë, was discovered in 2009.[13]

Michael Brown estimates that, with an absolute magnitude of 3.5 and a calculated diameter of approximately 700–800 kilometers (430–500 miles),[14][15] it is likely a dwarf planet.[16] However, William M. Grundy et al. argue that objects 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.[17] It is not clear if Varda has a low or a high density.

Discovery and orbit

Polar and ecliptic view of the orbit of Varda.

Varda was discovered in March 2006, using imagery dated from 21 June 2003, by Jeffrey A. Larsen with the Spacewatch telescope as part of a United States Naval Academy Trident Scholar project.[18]

It orbits the Sun at a distance of 39.5–52.7 AU once every 313.1 years (over 114,000 days; semi-major axis of 46.1 AU). Its orbit has an eccentricity of 0.14 and an inclination of 21.5° with respect to the ecliptic.[1] (As of November 2019), Varda is 47.5 AU from the Sun.[12] It will come to perihelion around November 2096.[6] It has been observed 321 times over 23 oppositions, with precovery images back to 1980.[1][2]

Name

Names for Varda and its moon were announced on 16 January 2014. Varda (qya) is the queen of the Valar, creator of the stars, one of the most powerful servants of almighty Eru Ilúvatar in J. R. R. Tolkien's fictional mythology. Ilmarë is a chief of the Maiar and Varda's handmaiden.[2]

Planetary symbols are no longer much used in astronomy, so Varda never received a symbol in the astronomical literature. There is no standard symbol for Varda used by astrologers either. Zane Stein proposed a gleaming star as the symbol (Varda symbol (fixed width).svg).[19]

Satellite

Varda has at least one satellite, Ilmarë (or Varda I), which was discovered in 2009. It is estimated to be about 350 km in diameter (about 50% that of its primary), constituting 8% of the system mass, or 2×1019 kg, assuming its density and albedo the same as that of Varda.[lower-alpha 2]

The Varda–Ilmarë system is tightly bound, with a semimajor axis of 4809±39 km (about 12 Varda radii) and an orbital period of 5.75 days.

Physical properties

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 722+82
−76 km.[8] 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.[10][8] On the other hand, if the density or albedo of the satellite is lower than that of primary then the density of Varda will be higher up to 1.31 g/cm3.[8]

On 10 September 2018, Varda's projected diameter was measured to be 766±6 km via a stellar occultation, with a projected oblateness of 0.066±0.047. The equivalent diameter is 740 km, consistent with previous measurements.[7] Given Varda's equivalent diameter derived from the occultation, its geometric albedo is measured at 0.099, making it as dark as the large plutino 2003 AZ84.

The rotation period of Varda is unknown; it has been estimated at 5.61 hours in 2015,[8] and more recently (in 2020) as either 4.76, 5.91 (the most likely value), 7.87 hours, or twice those values.[7] The large uncertainty in Varda's rotation period yields various solutions for its density and true oblateness; given a most likely rotation period of 5.91 or 11.82 hours, its bulk density and true oblateness could be either 1.78±0.06 g/cm3 and 0.235 or 1.23 g/cm3 and 0.080, respectively.[7]

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.[citation needed]

See also

Notes

  1. ↑ Assuming equal albedos for the primary and the secondary
  2. ↑ 2.0 2.1 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 of (2.664±0.064)×1020 kg.[8]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 "JPL Small-Body Database Browser: 174567 Varda (2003 MW12)". Jet Propulsion Laboratory. 30 May 2019. https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2174567. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "174567 Varda (2003 MW12)". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=174567. 
  3. ↑ "List of Transneptunian Objects". Minor Planet Center. https://minorplanetcenter.net/iau/lists/TNOs.html. 
  4. ↑ "MPEC 2009-P26 :Distant Minor Planets (2009 AUG. 17.0 TT)". Minor Planet Center. 2009-08-07. http://www.cfa.harvard.edu/mpec/K09/K09P26.html. 
  5. ↑ Marc W. Buie. "Orbit Fit and Astrometric record for 174567". SwRI (Space Science Department). http://www.boulder.swri.edu/~buie/kbo/astrom/174567.html. 
  6. ↑ 6.0 6.1 JPL Horizons Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 3-sigma.)
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 Souami, D.Expression error: Unrecognized word "etal". (August 2020). "A multi-chord stellar occultation by the large trans-Neptunian object (174567) Varda". Astronomy & Astrophysics 643: A125. doi:10.1051/0004-6361/202038526. Bibcode: 2020A&A...643A.125S. 
  8. ↑ 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 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". Icarus 257: 130–138. doi:10.1016/j.icarus.2015.04.036. Bibcode: 2015Icar..257..130G. 
  9. ↑ 9.0 9.1 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. doi:10.1051/0004-6361/201423567. Bibcode: 2014A&A...569A...3T. 
  10. ↑ 10.0 10.1 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". Astronomy & Astrophysics 541: 17. doi:10.1051/0004-6361/201118743. Bibcode: 2012A&A...541A..94V. 
  11. ↑ Tegler, S. C.; Romanishin, R. W.; Consolmalgo, J. S. (December 2016). "Two Color Populations of Kuiper Belt and Centaur Objects and the Smaller Orbital Inclinations of Red Centaur Objects". The Astronomical Journal 152 (6): 13. doi:10.3847/0004-6256/152/6/210. Bibcode: 2016AJ....152..210T. 
  12. ↑ 12.0 12.1 "AstDys (174567) Varda Ephemerides". Department of Mathematics, University of Pisa, Italy. https://newton.spacedys.com/astdys/index.php?pc=1.1.3.0&n=Varda. 
  13. ↑ Johnston, Wm. Robert (31 January 2015). "Asteroids with Satellites Database – (174567) Varda and Ilmare". Johnston's Archive. http://www.johnstonsarchive.net/astro/astmoons/am-174567.html. 
  14. ↑ Ceravolo, D.; Ceravolo, P. (26 July 2019). "(174567) Varda, 2018 September 10 occultation". http://www.asteroidoccultation.com/observations/Results/Reviewed/Data2018/20180910_VardaProfile.gif. 
  15. ↑ Braga-Ribas, Felipe; Sicardy, Bruno; Assafin, Marcelo; Ortiz, José-Luis; Camargo, Julio; Desmars, Josselin (September 2019). "The stellar occultation by the TNO (174567) Varda of September 10, 2018: size, shape and atmospheric constraints". EPSC-DPS Joint Meeting 2019. 13. European Planetary Science Congress. https://meetingorganizer.copernicus.org/EPSC-DPS2019/EPSC-DPS2019-1076-2.pdf. Retrieved 14 October 2019. 
  16. ↑ Brown, Michael E.. "How many dwarf planets are there in the outer solar system?". California Institute of Technology. http://web.gps.caltech.edu/~mbrown/dps.html. 
  17. ↑ 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,
  18. ↑ Larsen, Jeffrey A. et al. (2007). "The Search for Distant Objects in the Solar System Using Spacewatch". The Astronomical Journal 133 (4): 1247–1270. doi:10.1086/511155. Bibcode: 2007AJ....133.1247L. 
  19. ↑ Miller, Kirk (26 October 2021). "Unicode request for dwarf-planet symbols". https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf. 

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