174567 Varda

Discovery and orbit

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.

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. , Varda is 47.5 AU from the Sun. It will come to perihelion around November 2096. It has been observed 321 times over 23 oppositions, with precovery images back to 1980.

Name

The names for Varda and its moon were announced by the Minor Planets Center on 16 January 2014. Varda () 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.

The use of planetary symbols is rare in modern 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 ([[File:Varda symbol (fixed width).svg|16px]]).

Satellite

Main article: Ilmarë

Varda has one known satellite, Ilmarë (formal designation 174567 Varda I), which was discovered in 2009. It is estimated to be about 403 km in diameter (about 50% that of its primary), constituting 8% of the system mass, or , assuming its density and albedo are the same as that of Varda.

The Varda–Ilmarë system is tightly bound, with a semi-major axis of (about 12 Varda radii) and an orbital period of 5.75 days.

Physical characteristics

Based on its apparent brightness and assumed albedo, the estimated combined size of the Varda–Ilmarë system is , with the size of the primary estimated at . The total mass of the binary system is approximately . The density of both the primary and the satellite is estimated at , assuming that they have equal density. 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 .

On 10 September 2018, Varda's projected diameter was measured to be via a stellar occultation, with a projected oblateness of . The equivalent diameter is 740 km, consistent with previous measurements. 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 208996 Achlys.

The rotation period of Varda is unknown; it has been estimated at 5.61 hours in 2015, and more recently (in 2020) as either 4.76, 5.91 (the most likely value), 7.87 hours, or twice those values. 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 and or and , respectively.

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.

Notes

References

References

1. (30 May 2019). "JPL Small-Body Database Browser: 174567 Varda (2003 MW12)". [[Jet Propulsion Laboratory]].
2. "(174567) Varda = 2003 MW12". Minor Planet Center.
3. "List of Transneptunian Objects". Minor Planet Center.
4. Johnston, Wm. Robert. (31 January 2015). "Asteroids with Satellites Database – (174567) Varda and Ilmare". Johnston's Archive.
5. (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]].
6. (September 2015). "The mutual orbit, mass, and density of the large transneptunian binary system Varda and Ilmarë". Icarus.
7. (September 2014). "Rotational properties of the binary and non-binary populations in the trans-Neptunian belt". Astronomy and Astrophysics.
8. Marc W. Buie. "Orbit Fit and Astrometric record for 174567". SwRI (Space Science Department).
9. "AstDys (174567) Varda Ephemerides". Department of Mathematics, University of Pisa, Italy.
10. Larsen, Jeffrey A.. (2007). "The Search for Distant Objects in the Solar System Using Spacewatch". The Astronomical Journal.
11. (December 2016). "Two Color Populations of Kuiper Belt and Centaur Objects and the Smaller Orbital Inclinations of Red Centaur Objects". The Astronomical Journal.
12. (August 2020). "A multi-chord stellar occultation by the large trans-Neptunian object (174567) Varda". Astronomy & Astrophysics.
13. [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2003MW12 JPL Horizons] Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is [[3-sigma]].)
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 ({{mp. (229762) 2007 UK. 126)', ''Icarus'' [http://www2.lowell.edu/~grundy/abstracts/2019.G-G.html (forthcoming, available online 30 March 2019)] {{Webarchive. link. (7 April 2019 DOI: 10.1016/j.icarus.2018.12.037,)
15. Miller, Kirk. (26 October 2021). "Unicode request for dwarf-planet symbols".