The names ǂKá̦gára and ǃHãunu are from the mythology of the ǀXam people of South Africa. ǂKá̦gára (also rendered ǂKaʻgara) and his brother-in-law ǃHãunu fought an epic battle in the east using thunder and lightning, producing mountainous clouds and rain. The conflict was fought over ǂKá̦gára's returning his younger sister, ǃHãunu's wife, to their parents.[2][5] The names were approved and an official naming citation was published on 16 June 2021 by the International Astronomical Union's Working Group on Small Body Nomenclature.[6]
If the two bodies are spheres with equal density, then mutual 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]
Formation
Prograde orbits dominate tight binary systems such as 469705 ǂKá̦gára, those with satellite semimajor axes less than about 5% of their Hill radii. Grundy et 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.
469705 ǂKá̦gára has one known satellite, ǃHãunu. The magnitude difference between ǂKá̦gára and ǃHãunu is 0.59 mag. This corresponds to a difference in diameter of 13%, if the two bodies have the same albedo.[2]
The system mass is (2.18±0.12)×1018 kg, and, given the albedo, the bodies are equivalent to a single sphere of diameter 174+27 −32 km. This corresponds to a density of 1.1+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 are 138+21 −25 km and 122+16 −19 km.[2]
Notes
^Bleek & Lloyd wrote ⟨ǂk⟩ when the posterior release of the click was audible. Based on the sounds attested in the closely related language Nǁng, this [ǂ͡k] may therefore represent a palatal pulmonic-contour click, though this is not certain.
^Based on the co-occurrence of the letter ⟨H⟩ for aspiration of the click and the tilde for nasalization on the following vowel, together with the patterns of sounds in Nǁng, it is suspected that the click in ǃHãunu has delayed aspiration (i.e., is a long, aspirated, nasalized click), rather than a simple IPA:[ǃʰə̃unu], though again this is not certain.
