.png) Gǃkúnǁʼhòmdímà and its satellite Gǃòʼé ǃHú, imaged by theHubble Space Telescope on 2 January 2018 | |
| Discovery[1][2][3] | |
|---|---|
| Discovered by | M. E. Schwamb M. E. Brown D. L. Rabinowitz |
| Discovery site | Palomar Obs. |
| Discovery date | 19 October 2007 |
| Designations | |
| (229762) Gǃkúnǁʼhòmdímà | |
| Pronunciation | |
Named after | Gǃkúnǁʼhòmdímà[4] (San mythology) |
| 2007 UK126 | |
| Symbol | .svg) (astrological) |
| Orbital characteristics[5] | |
| Epoch 27 April 2019 (JD 2458600.5) | |
| Uncertainty parameter 2 · 3[1] | |
| Observation arc | 36.16yr (13,209 d) |
| Earliestprecovery date | 16 August 1982[1] |
| Aphelion | 108.058 AU (16.1652 Tm) |
| Perihelion | 37.5449328 AU (5.61664200 Tm) |
| 72.8013046 AU (10.89092015 Tm) | |
| Eccentricity | 0.4843 |
| 620.17 yr (226,517 d) | |
| 344.21° | |
| 0° 0m 5.76s / day | |
| Inclination | 23.378° |
| 131.09° | |
| ≈ 24 February 2046[8] ±1 days | |
| 346.88° | |
| Knownsatellites | 1 (Gǃòʼé ǃHú)[9] |
| Physical characteristics | |
| Dimensions | 678.0±11 ×611.4±18 km occultation[10] |
| 642±28[10] 599–629 km[11] 638+24 −12 km sphere-equivalent (elliptical fit)[12] | |
| Flattening | 0.105+0.05 −0.04[12] 0.118+0.055 −0.048[12] |
| Mass | (1.361±0.033)×1020 kg[4] (total system mass) |
Meandensity | 1.04±0.17 g/cm3, based on an effective diameter of632±34 km[4] |
| possibly11.05 h,[13] within 11 to 41 hours[4] | |
| 0.142±0.015[10] 0.150±0.016[11] 0.159+0.007 −0.013[12] | |
| Temperature | 50–55 K max.[11] |
| V–R=0.62±0.05[14] V–I=1.028±0.027[4] | |
| 20.8[3] | |
| HV=3.69±0.04; HR=3.07±0.04[11] | |
229762 Gǃkúnǁʼhòmdímà (provisional designation2007 UK126) is atrans-Neptunian object andbinary system from the extendedscattered disc, located in the outermost region of theSolar System.[15] It was discovered on 19 October 2007 by American astronomersMegan Schwamb,Michael Brown, andDavid Rabinowitz at thePalomar Observatory in California[1] and measures approximately 600 kilometers (400 miles) in diameter. This medium-sized TNO appears to be representative of a class of mid-sized objects under approximately 1000 km that have not collapsed into fully solid bodies. Its 100-kilometermoon was discovered by Keith Noll, Will Grundy, and colleagues with theHubble Space Telescope in 2008,[16][7][9][17] and named Gǃòʼé ǃHú.
The nameGǃkúnǁʼhòmdímà is from theJuǀʼhoansi (ǃKung) people of Namibia. Gǃkúnǁʼhòmdímà is the beautifulaardvark girl of Juǀʼhoan mythology, who sometimes appears in the stories of otherSan peoples as a python girl or elephant girl; she defends her people and punishes wrongdoers usinggǁámígǁàmì spines,[18] a rain-cloud full of hail, and her magicaloryx horn.[4] The name "Gǃkúnǁʼhòmdímà" derives fromgǃkún 'aardvark',ǁʼhòm mà 'young woman' and the feminine suffixdí. The moonGǃòʼé ǃHú is named after her horn: it means simply 'oryx' (gǃòʼé) 'horn' (ǃhú).[19]
In theJuǀʼhoan language, the planetoid and moon names are pronounced[ᶢᵏǃ͡χʼṹᵑ̊ǁʰòmdímà]ⓘ and[ᶢǃòˀéǃʰú]ⓘ, respectively. Usually, when speaking English, theclick consonants in words from Juǀʼhoan and other San languages are simply ignored (much asXhosa is pronounced/ˈkoʊzə/ (KOH-zə) rather than[ǁʰosa]), resulting in/ˌɡuːnhoʊmˈdiːmə/ (GOON-hohm-DEE-mə) forGǃkúnǁʼhòmdímà and/ˌɡoʊ.eɪˈhuː/ (GOH-ay-HOO) or/ˌɡoʊ.eɪˈkuː/ (GOH-ay-KOO) forGǃòʼé ǃHú.
ASCII renderings of the names would be⟨G!kun||'homdima⟩ (or⟨G!kun//'homdima⟩) for the primary and⟨G!o'e !Hu⟩ or⟨G!o'e!hu⟩ for the secondary.[20]
The usage ofplanetary symbols is now discouraged in astronomy, so Gǃkúnǁʼhòmdímà never received a symbol in the astronomical literature. There is no standard symbol for Gǃkúnǁʼhòmdímà used by astrologers either. An aardvark's head (
) has been used.[21]
Gǃkúnǁʼhòmdímà orbits the Sun at a distance of 37.5–107.9 AU once every 620 years and 2 months (226,517 days;semi-major axis of 72.72 AU). Its orbit has aneccentricity of 0.48 and aninclination of 23° with respect to theecliptic.[5] It is ascattered-disc object.[1]
An eccentricity of 0.48 suggests that it was gravitationallyscattered into its current eccentric orbit. It will come toperihelion in February 2046, andmutual occultation events with its satellite will begin in late 2050 and last most of that decade.[4] It has a brightabsolute magnitude of 3.7,[2] and has been observed 178 times over 16oppositions withprecovery images back to August 1982.[5]
Stellar occultation events indicate that Gǃkúnǁʼhòmdímà has an effective (equivalent-sphere) diameter of 600–670 km, but is not spherical. Due to complications from its non-spherical shape, the rotational period cannot be definitely determined from currentlight-curve data, which has an amplitude of Δm = 0.03 ± 0.01 mag, but the simplest solution is 11.05 hours.[13] It is almost certainly between that and 41 hours. The system mass is(1.36±0.03)×1020 kg, about 2% that of Earth's moon and a bit more than Saturn's moonEnceladus. The geometric albedo of Gǃkúnǁʼhòmdímà is approximately 0.15, and its bulk density is approximately1 g/cm3.[4] The satellite Gǃòʼé ǃHú is unlikely to comprise more than 1% or so of the total.
Grundy et al. propose that the low density and albedo of Gǃkúnǁʼhòmdímà, combined with the fact that TNOs both larger and smaller – including comets – have a substantial fraction of rock in their composition, indicate that objects such as Gǃkúnǁʼhòmdímà and174567 Varda (in the size range of 400–1000 km, with albedos less than ≈0.2 and densities of ≈1.2 g/cm3 or less) retain a degree of porosity in their physical structure, having never collapsed and differentiated into planetary bodies like higher density or higher albedo (and thus presumably resurfaced)90482 Orcus and50000 Quaoar, or at best are only partially differentiated; such objects would never have been in hydrostatic equilibrium and would not be dwarf planets at present.[4]
Gǃkúnǁʼhòmdímà exhibits an unusual disparity of visible and near-infrared colors: it appears reddish at visible wavelengths (V–R=0.62) while it appears bluer in the near-infrared (V–I=1.09). Hence, it does not fall within the fourproposed taxonomic classes for TNO colors. Two other TNOs, namely(26375) 1999 DE9 and(145452) 2005 RN43, exhibit this same color behavior, implying an additional color group among TNOs.[14]
| Discovery | |
|---|---|
| Discovered by | Noll et al.[16] |
| Discovery date | 2008 |
| Designations | |
Designation | (229762) Gǃkúnǁʼhòmdímà I |
| Pronunciation | English:/ˌɡoʊ.eɪˈkuː/ Juǀʼhoan:[ᶢǃòˀéᵏǃʰú]ⓘ |
| Orbital characteristics[4] | |
| 6035±48 km | |
| Eccentricity | 0.0236±0.0066 |
| 11.31473±0.00016 d (prograde) | |
| Inclination | 43.75°±0.38° (to J2000 equatorial frame) |
| Physical characteristics | |
| 71±4 km[4] | |
Spectral type | V–I=1.803±0.084[4] |
Gǃkúnǁʼhòmdímà has one known satellite,Gǃòʼé ǃHú, which is one of the reddest known TNOs.[4] Size and mass can only be inferred. The magnitude difference between the two is3.24±0.04 mag. This would correspond to a difference in diameter by a factor of4.45±0.08, assuming the same albedo.[4] Red satellites often have lower albedos than their primaries, though it is not known if that is the case with this moon. Such uncertainties do not affect density calculations of Gǃkúnǁʼhòmdímà, as Gǃòʼé ǃHú has only about 1% the total volume, and therefore is less important than the uncertainties in Gǃkúnǁʼhòmdímà's diameter.[4]
{{cite book}}: CS1 maint: multiple names: authors list (link)
| Planetary satellites of |    | |
|---|---|---|
| Dwarf planet satellites of | ||
| Minor-planet moons | ||
| Ranked by size | ||
| Consensus | _(cropped).jpg)  | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Candidate (for TNOs, D+1σ ≥ 700 km or H ≤ 4.2) |
| ||||||||||||
