174567 Varda
Trans-Neptunian object
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174567 Varda (provisional designation 2003 MW12) is a large binary trans-Neptunian object in the hot classical population of the Kuiper belt, located in the outermost region of the Solar System.[1] Its moon, Ilmarë, was discovered in 2009.[12]
Hubble Space Telescope image of Varda and its satellite Ilmarë, taken in 2010 and 2011 | |
| Discovery[1][2][3] | |
|---|---|
| Discovered by | J. A. Larsen |
| Discovery site | Kitt Peak National Obs. |
| Discovery date | 21 June 2003 |
| Designations | |
Designation | (174567) Varda |
| Pronunciation | /ËvÉËrdÉ/ |
Named after | Varda (figure by J. R. R. Tolkien)[2] |
| 2003 MW12 | |
| TNO[1] · classical (hot)[4] detached[5] · distant[2] | |
| Symbol | .svg){kind=small} (astrological) |
| Orbital characteristics[1] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 39.12 yr (14,290 d) |
| Earliest precovery date | 19 March 1980 |
| Aphelion | 52.711 AU |
| Perihelion | 39.510 AU |
| 46.110 AU | |
| Eccentricity | 0.14315 |
| 313.12 yr (114,366 d) | |
| 275.208° | |
| 0° 0m 11.332s / day | |
| Inclination | 21.511° |
| 184.151° | |
| â 1 November 2096[6] ±4 days | |
| 180.072° | |
| Known satellites | 1 (Ilmarë) |
| Physical characteristics | |
| 740±14 km (area equivalent)[7] | |
| Flattening | 0.080±0.049 (for period of 11.82 h)[7] or 0.235±0.050 (for period of 5.91 h) (most probable)[7] |
| Mass | (2.44±0.06)Ã1020 kg[7][a] |
Mean density | 1.23±0.04 g/cm3 (for period of 11.82 h)[7] 1.78±0.06 g/cm3 (for period of 5.91 h) (the most probable)[7] |
| 5.61 h[8] or 5.91 h (the most probable) or 4.76 h or 7.87 h (single-peaked)[9] 11.82 h or 9.52 h, or 15.74 h. (double-peaked)[9] | |
| Albedo | 0.099±0.002 (geometric)[7] 0.102±0.024[4] |
Spectral type | IR (moderately red)[8] BâV=0.886±0.025[8] VâR=0.55±0.02[10] VâI=1.156±0.029[8] |
| 20.5[11] | |
| 3.81±0.01 (primary)[7] 3.097±0.060[8] 3.46[1] | |
Varda is a possible dwarf planet. Objects in the size range of 400â1000 km, such as Varda, have likely never compressed into fully solid bodies, let alone differentiated, and so are highly unlikely to be dwarf planets.[13] However, density calculations for Varda are ambiguous. It is not clear if Varda's density is high enough to compressed into a fully solid body. Its low albedo is however consistent with a lack of the geological activity that is thought to be typical of dwarf planets.[13]
History
Discovery
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.[14]
Name
The names for Varda and its moon were announced by the Minor Planets Center on 16 January 2014. Varda (Quenya: [Ëvarda]) 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]
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 (.svg){kind=small}
).[15]
Orbit and classification
Orbital characteristics, observations and precoveries
Varda orbits the Sun at a distance of 39.5â52.7 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[update], Varda is 47.5 AU from the Sun.[11] 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]
Classification
Varda is located in the classical region of the Kuiper belt 39â48 AU from the Sun, and is thus classified as a typical member of a classical Kuiper belt object (also known as a "cubewano").[4] The high orbital inclination of Varda makes it a dynamically "hot" member of the classical Kuiper belt.[4] The hot classical Kuiper belt objects are believed to have been scattered by Neptune's gravitational influence during the Solar System's early history.[16]:â230â
Physical characteristics
Based on its apparent brightness and assumed albedo, the estimated combined size of the VardaâIlmarë system is 792+91
â84 km, with the size of the primary estimated at 722+82
â76 km.[8] The total mass of the binary system is approximately 2.66Ã1020 kg. The density of both the primary and the satellite is estimated at 1.24 g/cm3, assuming that they have equal density.[4][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 area 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 208996 Achlys.
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±0.050 or 1.23 g/cm3 and 0.080±0.049, 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]
Satellite
Varda has one known satellite, Ilmarë,[b] formal designation (174567) Varda I. Ilmarë was discovered by Keith Noll in 2009, at a separation of about 0.12 arcsec, using discovery images taken by the Hubble Space Telescope on 26 April 2009, the discovery was reported in 2011.[17] It is approximately 403 km in diameter according to the ALMA study done in 2025,[18] making it the fourth-largest known moon of a trans-Neptunian object, after Charon,[19] Dysnomia,[20] and Vanth.[21] Under the assumption of a lower density of 0.7 g/cm3, which is thought to be more typical that of trans-Neptunian objects in the ~400 km size range, the Ilmarë-to-Varda mass ratio would be around 0.11:1.[18]
Orbital characteristics
Ilmarë orbits Varda at a distance of 4805±35 km or 4812±35 km[8] and an eccentricity of 0.0181±0.0045 or 0.0247±0.0048 respectively.[8] Ilmarë has an orbital period of approximately 5.75058±0.00015 d.[8] Ilmarë's orbit has an inclination of 101.0±1.9° or 85.1±1.8° with respect to the ecliptic.[8]
See also
- 55565 Aya â a similar trans-Neptunian object by orbit, size, and color
- 532037 Chiminigagua â a trans-Neptunian object that has a diameter similar to Varda (742 km)
