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

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 as ...

, located in the Hecuba gap in the outermost region of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, c ...

. The carbonaceous asteroid measures approximately in diameter and has a rotation period of 6.9 hours. It was discovered on 31 July 1935, by South-African astronomer Cyril Jackson at Union Observatory 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 Cap ...

in South Africa and Namibia.

Orbit and classification

''Griqua'' is an asteroid in a

ary orbit (ACO), with no observable coma 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 ...

of 2.95, below the threshold of 3.0 defined for main-belt asteroids. ACO's may be

extinct comet An extinct comet is a comet that has expelled most of its volatile ice and has little left to form a tail and coma. In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface la ...

s. It is the namesake and largest member of the small dynamical

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

resonant Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscilla ...

zone with the gas giant

Jupiter Jupiter is the fifth planet from the Sun and the 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 slightly less than one-thousandth t ...

(2/1J). ''Griqua'' itself is

background asteroid 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 ...

s and does not belong to any known asteroid family. 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 of 3.22 AU). Its orbit has a high

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 0.37 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 reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 24 ° 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 agains ...

. 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 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 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 ...

, ''Griqua''

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

is ambiguous, closest to a common

C-type asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

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-t ...

(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, ...

in both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2).

Rotation period

In November 2000, a rotational

lightcurve 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 ...

of ''Griqua'' was obtained from photometric observations by Colin Bembrick at the Mount Tarana Observatory in Australia. Lightcurve analysis gave a well-defined rotation period of 6.907 hours with a brightness variation of 0.25

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

(). In 2009, follow-up observations by Jean and Milan Strajnic , Alain Klotz and

Raoul Behrend 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 num ...

as well as observations in the S-band by astronomers at the Palomar Transient Factory 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 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 201 ...

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 201 ...

, ''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 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 that refl ...

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 astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

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 ch ...

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 ''mino ...

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 Khoekhoen (singular Khoekhoe) (or Khoikhoi in the former orthography; formerly also '' Hottentots''"Hottentot, n. and adj." ''OED Online'', Oxford University Press, March 2018, www.oed.com/view/Entry/88829. Accessed 13 May 2018. Citing G. S. ...

descent in Griqualand in South Africa and Namibia. The official naming citation was mentioned in ''

The Names of the Minor Planets Paul Herget (January 30, 1908 – August 27, 1981) was an American astronomer and director of the Cincinnati Observatory, who established the Minor Planet Center after World War II. Career Herget taught astronomy at the University of Cincinna ...

'' by

Paul Herget Paul Herget (January 30, 1908 – August 27, 1981) was an American astronomer and director of the Cincinnati Observatory, who established the Minor Planet Center after World War II. Career Herget taught astronomy at the University of Cincinn ...

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