229762 Gǃkúnǁʼhòmdímà (provisional designation ) is a trans-Neptunian object and binary system from the extended

scattered disc The scattered disc (or scattered disk) is a distant circumstellar disc in the Solar System that is sparsely populated by icy small Solar System bodies, which are a subset of the broader family of trans-Neptunian objects. The scattered-disc obj ...

, located in the outermost region of the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. It was discovered on 19 October 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the

Palomar Observatory The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

in California and measures approximately 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-kilometer

moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

was discovered by Keith Noll, Will Grundy, and colleagues with the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

in 2008, and named Gǃòʼé ǃHú.

Names

The name ''Gǃkúnǁʼhòmdímà'' is from the Juǀʼhoansi ( ǃKung) people of Namibia. Gǃkúnǁʼhòmdímà is the beautiful

aardvark Aardvarks ( ; ''Orycteropus afer'') are medium-sized, burrowing, nocturnal mammals native to Africa. Aardvarks are the only living species of the family Orycteropodidae and the order Tubulidentata. They have a long proboscis, similar to a pi ...

girl of Juǀʼhoan mythology, who sometimes appears in the stories of other

San people The San peoples (also Saan), or Bushmen, are the members of any of the indigenous hunter-gatherer cultures of southern Africa, and the oldest surviving cultures of the region. They are thought to have diverged from other humans 100,000 to 200 ...

s as a python girl or elephant girl; she defends her people and punishes wrongdoers using ''gǁámígǁàmì'' spines, a rain-cloud full of hail, and her magical oryx horn. The name "Gǃkúnǁʼhòmdímà" derives from ''gǃkún'' 'aardvark', ''ǁʼhòm mà'' 'young woman' and the feminine suffix ''dí''. The moon Gǃòʼé ǃHú is named after her horn: it means simply 'oryx' (''gǃòʼé'') 'horn' (''ǃhú''). In the

Juǀʼhoan language Juǀʼhoan ( , ), also known as Southern or Southeastern ǃKung or ǃXun, is the southern variety of the ǃKung dialect continuum, spoken in northeastern Namibia and the Northwest District of Botswana by San Bushmen who largely identify themse ...

, the planetoid and moon names are pronounced and , respectively. Usually, when speaking English, the

click consonant Click consonants, or clicks, are speech sounds that occur as consonants in many languages of Southern Africa and in three languages of East Africa. Examples familiar to English-speakers are the '' tut-tut'' (British spelling) or '' tsk! tsk!' ...

s in words from Juǀʼhoan and other San languages are simply ignored (much as '' Xhosa'' is pronounced () rather than ), resulting in () for ''Gǃkúnǁʼhòmdímà'' and () or () for ''Gǃòʼé ǃHú''.

ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...

renderings of the names would be (or ) for the primary and or for the secondary.Minor Planet Names: Alphabetical List
/ref> The usage of

planetary symbol Planetary symbols are used in astrological symbol, astrology and traditionally in astronomical symbol, astronomy to represent a classical planet (which includes the Sun and the Moon) or one of the modern planets. The classical symbols were also use ...

s 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.

Orbit

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 In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

of 72.72 AU). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.48 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 23 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. It is a scattered-disc object. An eccentricity of 0.48 suggests that it was gravitationally scattered into its current eccentric orbit. It will come to

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

in February 2046, and mutual occultation events with its satellite will begin in late 2050 and last most of that decade. It has a bright absolute magnitude of 3.7, and has been observed 178 times over 16 oppositions with precovery images back to August 1982.

Physical characteristics

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 current light-curve data, which has an amplitude of Δm = 0.03 ± 0.01 mag, but the simplest solution is 11.05 hours. It is almost certainly between that and 41 hours. The system mass is , about 2% that of Earth's moon and a bit more than Saturn's moon Enceladus. The geometric albedo of Gǃkúnǁʼhòmdímà is approximately 0.15, and its bulk density is approximately . 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 and 174567 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 and

50000 Quaoar Quaoar ( minor-planet designation: 50000 Quaoar) is a ringed dwarf planet in the Kuiper Belt, a ring of many icy planetesimals beyond Neptune. It has an elongated ellipsoidal shape with an average diameter of , about half the size of the d ...

, or at best are only partially differentiated; such objects would never have been in hydrostatic equilibrium and would not be dwarf planets at present. 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 four proposed taxonomic classes for TNO colors. Two other TNOs, namely and , exhibit this same color behavior, implying an additional color group among TNOs.

Satellite

Gǃkúnǁʼhòmdímà has one known satellite, Gǃòʼé ǃHú, which is one of the reddest known TNOs. Size and mass can only be inferred. The magnitude difference between the two is mag. This would correspond to a difference in diameter by a factor of , assuming the same albedo. 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.

References

External links