1362 Griqua, provisional designation is a dark, Jupiter-resonant background

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

on an eccentric,

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

ary-like orbit and the namesake of the

Griqua group A Hecuba-gap asteroid is a member of a dynamical group of resonant asteroids located in the Hecuba gap at 3.27 AU – one of the largest Kirkwood gaps in the asteroid belt, which is considered the borderline separating the outer main belt ast ...

, located in the

Hecuba gap A Kirkwood gap is a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter. For example, there a ...

in the outermost region of the asteroid belt. The carbonaceous asteroid measures approximately in diameter and has a

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

of 6.9 hours. It was discovered on 31 July 1935, by South-African astronomer Cyril Jackson at

Union Observatory Union Observatory also known as Johannesburg Observatory ( 078) is a defunct astronomical observatory in Johannesburg, South Africa that was operated between 1903 and 1971. It is located on Observatory Ridge, the city's highest point at 1,808 met ...

in Johannesburg. The asteroid was named after the

Griqua people The Griquas (; af, Griekwa, often confused with ''!Orana'', which is written as ''Korana'' or ''Koranna'') are a subgroup of heterogeneous former Khoe-speaking nations in Southern Africa with a unique origin in the early history of the Cape ...

in South Africa and Namibia.

Orbit and classification

''Griqua'' is an asteroid in a

ary orbit (ACO), with no observable

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

but with a

Tisserand's parameter Tisserand's parameter (or Tisserand's invariant) is a value calculated from several orbital elements (semi-major axis, orbital eccentricity and inclination) of a relatively small object and a larger " perturbing body". It is used to distinguish dif ...

of 2.95, below the threshold of 3.0 defined for main-belt asteroids. ACO's may be extinct comets. It is the namesake and largest member of the small dynamical

(known as the "Griquas"), a ''marginally unstable'' group of asteroids observed in the

, a resonant zone with the gas giant

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

(2/1J). ''Griqua'' itself is background asteroids and does not belong to any known

asteroid family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An a ...

. This asteroid orbits the Sun in the outermost asteroid belt at a distance of 2.0–4.4 AU once every 5 years and 9 months (2,107 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 3.22 AU). Its orbit has a high eccentricity of 0.37 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 24 ° with respect to the ecliptic. The body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

begins with its first observation as at

Lowell Observatory Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark ...

in January 1931, more than 4 years prior to its official discovery observation at Johannesburg.

Groups in the Hecuba gap

The marginally unstable Griqua group includes 3688 Navajo, 4177 Kohman and 11665 Dirichlet, while the ''stable'' 2:1 resonant group are the "Zhongguos", named after

3789 Zhongguo 3789 Zhongguo, provisional designation ', is a resonant asteroid from outermost region of the asteroid belt, approximately in diameter. It was discovered in 1928 by Chinese astronomer Zhang Yuzhe at the Yerkes Observatory in Williams Bay, Wiscon ...

. The transition between these two groups, however, is not clear. The unnamed, third group in the Hecuba gap are ''strongly unstable''. Their largest members are the asteroids 1921 Pala, 1922 Zulu and 5201 Ferraz-Mello, as well as 5370 Taranis, 8373 Stephengould, and 9767 Midsomer Norton.

Physical characteristics

In the Tholen classification, ''Griqua'' spectral type is ambiguous, closest to a common C-type asteroid and somewhat similar to an primitive

P-type asteroid P-type asteroids are asteroids that have low albedo and a featureless reddish spectrum. It has been suggested that they have a composition of organic rich silicates, carbon and anhydrous silicates, possibly with water ice in their interior. P-type ...

(CP). The asteroid has also been characterized as a "brighter"

B-type asteroid B-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-group; the 'B' indicates these objects are spectrally blue. In the asteroid population, B-class objects can be found in the outer asteroid belt, an ...

in both the Tholen- and SMASS-like taxonomy of the

Small Solar System Objects Spectroscopic Survey An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiated ...

(S3OS2).

Rotation period

In November 2000, a rotational lightcurve of ''Griqua'' was obtained from photometric observations by Colin Bembrick at the Mount Tarana Observatory in Australia. Lightcurve analysis gave a well-defined

of 6.907 hours with a brightness variation of 0.25 magnitude (). In 2009, follow-up observations by Jean and Milan Strajnic ,

Alain Klotz This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 nu ...

and Raoul Behrend as well as observations in the S-band by astronomers at the

Palomar Transient Factory The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The projec ...

in California gave a concurring period of 6.891 and 6.9 hours with an amplitude of 0.23 and 0.24 magnitude, respectively (). The result supersedes a measurement of 7 hours made in the 1970s ().

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

, the Japanese Akari satellite and the NEOWISE mission of NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

, ''Griqua'' measures between 25.60 and 30 kilometers in diameter and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

between 0.0667 and 0.091. The ''Collaborative Asteroid Lightcurve Link'' adopts the results obtained by IRAS, that is, an albedo of 0.0667 with a diameter of 29.90 kilometers based on an

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 11.18, while fragmentary

radiometric Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which cha ...

observations in the 1970s determined a diameter of 31.0 kilometer and a derived albedo of 0.055 (TRIAD).

Naming

This

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

is named after the

Afrikaans Afrikaans (, ) is a West Germanic language that evolved in the Dutch Cape Colony from the Dutch vernacular of Holland proper (i.e., the Hollandic dialect) used by Dutch, French, and German settlers and their enslaved people. Afrikaans gra ...

-speaking

, a mixed tribe of Bushman and Khoikhoi descent in Griqualand in South Africa and Namibia. The official naming citation was mentioned in '' The Names of the Minor Planets'' by Paul Herget in 1955 ().

Notes

References

External links

Asteroids in Cometary Orbits (ACOs)
''

Instituto de Astrofísica de Canarias The Instituto de Astrofísica de Canarias (IAC) is an astrophysical research institute located in the Canary Islands, Spain. It was founded in 1975 at the University of La Laguna. It operates two astronomical observatories in the Canary Islands: ...

''
Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend

– Minor Planet Center * * {{DEFAULTSORT:Griqua 001362 001362 Discoveries by Cyril Jackson (astronomer) Named minor planets 001362 19350731