229762 Gǃkúnǁʼhòmdímà (provisional designation ) is a

trans-Neptunian object A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au). Typically, ...

and

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

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 objec ...

, 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 "Solar S ...

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

David Rabinowitz David Lincoln Rabinowitz (born 1960) is an American astronomer, discoverer of minor planets and researcher at Yale University. Career David Rabinowitz has built CCD cameras and software for the detection of near-Earth and Kuiper belt obje ...

at the

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. 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 is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

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

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

in 2008, and named Gǃòʼé ǃHú.

Names

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

aardvark The aardvark ( ; ''Orycteropus afer'') is a medium-sized, burrowing, nocturnal mammal native to Africa. It is the only living species of the order Tubulidentata, although other prehistoric species and genera of Tubulidentata are known. Unlike ...

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

San people The San peoples (also Saan), or Bushmen, are members of various Khoe, Tuu, or Kxʼa-speaking indigenous hunter-gatherer cultures that are the first cultures of Southern Africa, and whose territories span Botswana, Namibia, Angola, Zambia, ...

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 ''Oryx'' is a genus consisting of four large antelope species called oryxes. Their pelage is pale with contrasting dark markings in the face and on the legs, and their long horns are almost straight. The exception is the scimitar oryx, which l ...

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 themselv ...

, 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 Xhosa may refer to: * Xhosa people, a nation, and ethnic group, who live in south-central and southeasterly region of South Africa * Xhosa language, one of the 11 official languages of South Africa, principally spoken by the Xhosa people See als ...

'' is pronounced () rather than ), resulting in () and () or ().

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...

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

Planetary symbol A planet symbol (or ''planetary symbol'') is a graphical symbol used in astrology and astronomy to represent a classical planet (including the Sun and the Moon) or one of the modern planets. The symbols were also used in alchemy to represent the me ...

s are no longer much used 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 ( Gǃkunǁʼhomdima symbol

) 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 long ...

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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 23 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...

. It is a

Scattered-disc object 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 objec ...

. 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. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

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 Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 3.7, and has been observed 178 times over 16

oppositions ''Oppositions'' was an architectural journal produced by the Institute for Architecture and Urban Studies from 1973 to 1984. Many of its articles contributed to advancing architectural theory and many of its contributors became distinguished practi ...

with

precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of an object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This happens mos ...

images back to 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 In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular freq ...

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 Enceladus is the sixth-largest moon of Saturn (19th largest in the Solar System). It is about in diameter, about a tenth of that of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh, clean ice, making it one of the most refle ...

. The geometric albedo of Gǃkúnǁʼhòmdímà is approximately 0.15, and its bulk density 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 Orcus (minor-planet designation 90482 Orcus, provisional designation ) is a trans-Neptunian object, trans-Neptunian dwarf planet with a large moon, Vanth (moon), Vanth. It has a diameter of . The surface of Orcus is relatively bright with albed ...

and 50000 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. 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 so is less important than the uncertainties in Gǃkúnǁʼhòmdímà's diameter.

References

External links