 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 −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, withalbedos less than ≈0.2 and densities less than ≈1.2 g/cm3, 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 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 | ||
