 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 | /ˈvɑːrdə/ |
Named after | Varda (figure byJ. R. R. Tolkien)[2] |
| 2003 MW12 | |
| TNO[1] · classical (hot)[4] detached[5] · distant[2] | |
| Symbol | .svg) (astrological) |
| Orbital characteristics[1] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 39.12yr (14,290 d) |
| Earliestprecovery date | 19 March 1980 |
| Aphelion | 52.711AU |
| Perihelion | 39.510 AU |
| 46.110 AU | |
| Eccentricity | 0.14315 |
| 313.12yr (114,366d) | |
| 275.208° | |
| 0° 0m 11.332s / day | |
| Inclination | 21.511° |
| 184.151° | |
| ≈ 1 November 2096[6] ±4 days | |
| 180.072° | |
| Knownsatellites | 1 (Ilmarë) |
| Physical characteristics | |
| 740±14 km(area equivalent)[7] | |
| Flattening | 0.080±0.049(for period of 11.82 h)[7] or0.235±0.050(for period of 5.91 h)(most probable)[7] |
| Mass | (2.44±0.06)×1020 kg[7][a] |
Meandensity | 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] or5.91 h(the most probable) or4.76 h or7.87 h(single-peaked)[9] 11.82 h or9.52 h, or15.74 h.(double-peaked)[9] | |
| Albedo | 0.099±0.002(geometric)[7] 0.102±0.024[4] |
Spectral type | IR (moderately red)[8] B−V=0.886±0.025[8] V–R=0.55±0.02[10] V−I=1.156±0.029[8] |
| 20.5[11] | |
| 3.81±0.01(primary)[7] 3.097±0.060[8] 3.4[1] | |
174567 Varda (provisional designation2003 MW12) is a large binarytrans-Neptunian object in thehot classical population of theKuiper belt, located in the outermost region of theSolar System.[1] Itsmoon,Ilmarë, was discovered in 2009.[12]
Varda is a possibledwarf planet. Objects in the size range of 400–1000 km, such as Varda, have likely never compressed into fully solid bodies, let alonedifferentiated, and so are highly unlikely to bedwarf planets.[13] However,density calculations for Varda are ambiguous, and is not clear if Varda is above or below this estimated limit. Its lowalbedo is however consistent with a lack of the geological activity that is thought to be typical ofdwarf planets.[13]
Varda was discovered in March 2006, using imagery dated from 21 June 2003, byJeffrey A. Larsen with theSpacewatch telescope as part of a United States Naval Academy Trident Scholar project.[14]
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 aneccentricity of 0.14 and aninclination of 21.5° with respect to theecliptic.[1] As of November 2019[update], Varda is 47.5 AU from the Sun.[11] It will come toperihelion around November 2096.[6] It has been observed 321 times over 23oppositions, withprecovery images back to 1980.[1][2]
The names for Varda and its moon were announced by the Minor Planets Center on 16 January 2014.Varda (Quenya:[ˈvarda]) is the queen of theValar, creator of the stars, one of the most powerful servants of almightyEru Ilúvatar in J. R. R. Tolkien'sfictional mythology. Ilmarë is a chief of theMaiar and Varda's handmaiden.[2]
The use ofplanetary 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)
).[15]
Varda has one knownsatellite,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, or2×1019 kg, assuming its density and albedo are the same as that of Varda.[a]
The Varda–Ilmarë system is tightly bound, with a semi-major axis of4809±39 km (about 12 Varda radii) and an orbital period of 5.75 days.
Based on its apparent brightness and assumedalbedo, the estimated combinedsize of the Varda–Ilmarë system is792+91
−84 km, with thesize of the primary estimated at722+82
−76 km.[8] The totalmass of thebinary system is approximately2.66×1020 kg. Thedensity of both the primary and the satellite is estimated at1.24 g/cm3, assuming that they have equaldensity.[4][8] On the other hand, if thedensity oralbedo of the satellite is lower than that of primary then thedensity of Varda will be higher up to1.31 g/cm3.[8]
On 10 September 2018, Varda's projected diameter was measured to be766±6 km via a stellar occultation, with a projectedoblateness of0.066±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 largeplutino208996 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 either1.78±0.06 g/cm3 and0.235±0.050 or1.23 g/cm3 and0.080±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 ofmethanol ice.[citation needed]
| Consensus | _(cropped).jpg)  | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Candidate (for TNOs, D+1σ ≥ 700 km or H ≤ 4.0) |
| ||||||||||||
| Planetary satellites of |    | |
|---|---|---|
| Dwarf planet satellites of | ||
| Minor-planet moons | ||
| Ranked by size | ||
