| Discovery[1] | |
|---|---|
| Discovered by | C. Jackson |
| Discovery site | Johannesburg Obs. |
| Discovery date | 31 July 1935 |
| Designations | |
| (1362) Griqua | |
Named after | Griqua people[2] (South African tribe) |
| 1935 QG1 · 1931 BN | |
| main-belt · (outer)[3][4] Griqua[5] · background[6] ACO[7] | |
| Orbital characteristics[3] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 87.03yr (31,788 d) |
| Aphelion | 4.4123AU |
| Perihelion | 2.0213 AU |
| 3.2168 AU | |
| Eccentricity | 0.3716 |
| 5.77 yr (2,107 d) | |
| 16.650° | |
| 0° 10m 14.88s / day | |
| Inclination | 24.223° |
| 121.34° | |
| 261.82° | |
| TJupiter | 2.9490 |
| Physical characteristics | |
| 25.60±3.72 km[8] 26.936±0.363 km[9][10] 28.36±0.40 km[11] 29.90±1.5 km[12] 29.9±3.0 km[13] 30±3 km[14] 31.0 km(radiometric)[6] | |
| 6.891±0.0297 h[15] 6.9±0.1 h[16] 6.907±0.003 h[17] 7 h(poor)[18] | |
| 0.055(radiometric)[6] 0.0667±0.007[12] 0.07±0.01[14][13] 0.075±0.002[11] 0.082±0.013[9][10] 0.091±0.042[8] | |
| Tholen =CP[3][4] B(S3OS2)[7][19] U–B = 0.360[3] B–V = 0.720[3] | |
| 11.18[3][4][8][10][11][12][13][14] 11.18±0.10[20] 11.561±0.003(S)[15] | |
1362 Griqua, provisional designation1935 QG1 is a dark, Jupiter-resonant backgroundasteroid on an eccentric,cometary-like orbit and the namesake of theGriqua group, located in theHecuba gap in the outermost region of theasteroid belt.[5] The carbonaceous asteroid measures approximately 28 kilometers (17 miles) in diameter and has arotation period of 6.9 hours.[4] It was discovered on 31 July 1935, by South-African astronomerCyril Jackson atUnion Observatory in Johannesburg.[1] The asteroid was named after theGriqua people in South Africa and Namibia.[2]
Griqua is an asteroid in acometary orbit (ACO), with no observablecoma but with aTisserand's parameter of 2.95,[3] belowthe threshold of 3.0 defined for main-belt asteroids. ACO's may beextinct comets.[7] It is the namesake and largest member of the small dynamicalGriqua group (known as the "Griquas"), amarginally unstable group of asteroids observed in theHecuba gap, aresonant zone with the gas giantJupiter (2/1J).[5]Griqua itself isbackground asteroids and does not belong to any knownasteroid family.[6]
This asteroid orbits the Sun in theoutermost 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 higheccentricity of 0.37 and aninclination of 24° with respect to theecliptic.[3]
The body'sobservation arc begins with its first observation as1931 BN atLowell Observatory in January 1931, more than 4 years prior to its official discovery observation at Johannesburg.[1]
The marginally unstable Griqua group includes3688 Navajo,4177 Kohman and11665 Dirichlet, while thestable 2:1 resonant group are the "Zhongguos", named after3789 Zhongguo. The transition between these two groups, however, is not clear. The unnamed, third group in the Hecuba gap arestrongly unstable. Their largest members are the asteroids1921 Pala,1922 Zulu and5201 Ferraz-Mello, as well as5370 Taranis,8373 Stephengould, and9767 Midsomer Norton.[5]: 422, 423
In theTholen classification,Griqua'sspectral type is ambiguous, closest to a commonC-type asteroid and somewhat similar to an primitiveP-type asteroid (CP).[3][4] The asteroid has also been characterized as a "brighter"B-type asteroid in both the Tholen- and SMASS-like taxonomy of theSmall Solar System Objects Spectroscopic Survey (S3OS2).[7][19]
In November 2000, a rotationallightcurve ofGriqua was obtained fromphotometric observations by Colin Bembrick at theMount Tarana Observatory in Australia. Lightcurve analysis gave a well-definedrotation period of 6.907 hours with a brightness variation of 0.25magnitude (U=3).[17] In 2009, follow-up observations by Jean and Milan Strajnic (511),Alain Klotz andRaoul Behrend as well as observations in the S-band by astronomers at thePalomar 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 (U=2/2).[15][16] The result supersedes a measurement of 7 hours made in the 1970s (U=1).[18]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite and theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer,Griqua measures between 25.60 and 30 kilometers in diameter and its surface has analbedo between 0.0667 and 0.091.[8][9][10][11][12][13][14]
TheCollaborative 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 anabsolute magnitude of 11.18,[4] while fragmentaryradiometric observations in the 1970s determined a diameter of 31.0kilometer and a derived albedo of 0.055 (TRIAD).[6][a]
Thisminor planet is named after theAfrikaans-speakingGriqua people, a mixed tribe ofBushman andKhoikhoi descent in Griqualand in South Africa and Namibia. The official naming citation was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 24).[2]
