 StackedHubble Space Telescope images of ǂKá̦gára and ǃHãunu | |
| Discovery[1] | |
|---|---|
| Discovered by | Marc Buie |
| Discovery site | Kitt Peak Observatory |
| Discovery date | 11 March 2005 |
| Designations | |
| (469705) ǂKá̦gára | |
| Pronunciation |
|
Named after | ǂKá̦gára (ǀXam mythology)[2] |
| 2005 EF298 | |
| Cold classical KBO[2] | |
| Orbital characteristics[3][1] | |
| Epoch (JD 2460800.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 19.91yr (7271 d) |
| Aphelion | 47.884AU |
| Perihelion | 40.078 AU |
| 43.981 AU | |
| Eccentricity | 0.088 |
| 292.45 yr (106744.25 d) | |
| 118.059° | |
| 0.00337 0° 0m 0s / day | |
| Inclination | 2.86° |
| 117.968° | |
| 74.969° | |
| Knownsatellites | 1[4] |
| Physical characteristics | |
| 138+21 −25 km, assuming same albedo as ǃHãunu | |
| Mass | (1.29±0.07)×1018 kg, assuming same density and albedo as ǃHãunu |
Meandensity | 1.1+0.9 −0.4 g/cm3, assuming equal compositions of the bodies |
| HV =6.2±0.5 | |
469705 ǂKá̦gára (provisional designation2005 EF298) is atrans-Neptunian object andbinary system of the coreKuiper belt, located in the outermost region of theSolar System. It was discovered on 11 March 2005 by American astronomerMarc Buie at theKitt Peak Observatory in Arizona.[1] The primary body measures around 140 kilometers (90 miles) in diameter. Its 120-kilometer (75-mile)companionǃHãunu was discovered with theHubble Space Telescope in 2009. The ǂKá̦gára–ǃHãunu system is currently undergoingmutual occultation and eclipsing events in which one body casts a shadow on or obstructs the view of the other as seen from Earth.
The namesǂKá̦gára andǃHãunu are from the mythology of theǀXam people of South Africa.ǂKá̦gára (also rendered ǂKaʻgara) and his brother-in-lawǃHãunu fought an epic battle in the east using thunder and lightning, producing mountainous clouds and rain. The conflict was fought over ǂKá̦gára returning his younger sister, ǃHãunu's wife, to their parents.[2][5] The names were approved andan official naming citation was published on 16 June 2021 by theInternational Astronomical Union'sWorking Group on Small Body Nomenclature.[6]
In theǀXam language,ǂKá̦gára andǃHãunu are thought to have been pronounced[ǂ͡káˤɡáɾa]ⓘ[Note 1] and[ᵑ̊ǃʰəunu]ⓘ,[Note 2] respectively.[7]The initial lettersǂK and!H (and indeed the letterǀX in 'ǀXam') represent some of the manyclick consonants that characterize ǀXam and otherSan languages. Thediacritic under the first vowel inǂKá̦gára indicates that it is apharyngealized vowel, another characteristic of San languages. When pronounced in English, the click consonants in words from ǀXam and other San languages are usually ignored (much asXhosa is pronounced/ˈkoʊzə/ (KOH-zə) rather than[ǁʰosa]), resulting in/ˈkɑːʔɡɑːrə/ (KAHʼ-gar-ə) and/ˈhaʊnuː/ (HOW-noo).[citation needed]ASCII approximations of the names are=Ka'gara and!Haunu.
ǂKá̦gára is acold classical Kuiper belt object. It orbits the Sun at a distance of 44 AU once every 290 years. Its orbit has aneccentricity of 0.09 and aninclination of 3 degrees with respect to theecliptic.[3]
If the two bodies are spheres with equal density, thenmutual occultation events between ǂKá̦gára and its satellite ǃHãunu should have begun in 2015 and should continue until 2035. When ǂKá̦gára passes in front of ǃHãunu, events may last as long as 8 hours, but when ǃHãunu passes in front of ǂKá̦gára they are expected to last as long as 2 days. These latter events are only expected to occur from 2022 to 2027.[2]
Prograde orbits dominate tight binary systems such as ǂKá̦gára, those with satellite semimajor axes less than about 5% of theirHill radii. Grundyet al. suggest that this could be "the signature of planetesimal formation through gravitational collapse of local density enhancements such as caused by the streaming instability",[2] which has been suggested as the formative mechanism of the only visited planetesimal,486958 Arrokoth.
| Discovery | |
|---|---|
| Discovery date | 2009 |
| Designations | |
| Pronunciation |
|
Named after | ǃHãunu (San mythology)[2] |
| |
| Orbital characteristics[2][8][4] | |
| 7670±140 km | |
| Eccentricity | 0.694±0.013 |
| 128.107±0.027 d (prograde) | |
| Inclination |
|
| Physical characteristics | |
| 122+16 −19 km, assuming same albedo as ǂKá̦gára | |
| Mass | (0.89±0.05)×1018 kg, assuming same density and albedo as ǂKá̦gára |
| ΔH = 0.59 | |
ǂKá̦gára has one known satellite,ǃHãunu. The magnitude difference between ǂKá̦gára and ǃHãunu is0.59 mag. This corresponds to a difference in diameter of 13%, if the two bodies have the samealbedo.[2]
The system mass is(2.18±0.12)×1018 kg, and, given the albedo, the bodies are equivalent to a single sphere of diameter174+27
−32 km. This corresponds to a density of1.1+0.9
−0.4 g/cm3. This does not particularly constrain the composition of the bodies, as the error bars cover the densities of both small, porous bodies and larger, collapsed bodies. Assuming the two bodies have the same albedo and density, their masses are(1.29±0.07)×1018 kg and(0.89±0.05)×1018 kg, and their diameters are138+21
−25 km and122+16
−19 km.[2]
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| Ranked by size | ||