| Discovery[1] | |
|---|---|
| Discovered by | T. Seki |
| Discovery site | Geisei Obs. |
| Discovery date | 20 August 1990 |
| Designations | |
| (6244) Okamoto | |
Named after | Hiroshi Okamoto[1] (Japanese school teacher) |
| 1990 QF · 1952 SG1 1987 SL25 | |
| main-belt[1][2] · (inner) background[3] · Flora[4] | |
| Orbital characteristics[2] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 84.58yr (30,893 d) |
| Aphelion | 2.4888AU |
| Perihelion | 1.8319 AU |
| 2.1604 AU | |
| Eccentricity | 0.1520 |
| 3.18 yr (1,160 d) | |
| 208.44° | |
| 0° 18m 37.44s / day | |
| Inclination | 5.3954° |
| 331.33° | |
| 51.576° | |
| Knownsatellites | 1(D:1.67 kmP:20.32 h)[4][5][6] |
| Physical characteristics | |
| 4.59 km(derived)[4] 6.69 km(estimated)[5] | |
| 2.8958±0.00009 h[7] 2.8958±0.0001 h[6] 2.89585±0.00009 h[8] 2.899±0.003 h[9] | |
| 0.14(estimated)[5] 0.24(assumed)[4] | |
| S(assumed)[4] | |
| 13.41±0.04(R)[7] 13.5[2] 13.66±0.26[10] 13.9[4][11] | |
6244 Okamoto, provisional designation1990 QF, is a backgroundasteroid andbinary system from the inner regions of theasteroid belt, approximately 5 kilometers (3 miles) in diameter. It was discovered on 20 August 1990, by Japanese astronomerTsutomu Seki at theGeisei Observatory in Kōchi, Japan, and later named after Japanese school teacherHiroshi Okamoto.[1] The presumedS-type asteroid has a shortrotation period of 2.9 hours.[4] The discovery of itsminor-planet moon was announced in October 2006.[6]
Okamoto is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method to itsproper orbital elements.[3] Based on osculating Keplerianorbital elements, the asteroid has also been classified as a member of theFlora family (402), a giantasteroid family and the largest family of stony asteroids in the main-belt.[4]
It orbits the Sun in theinner asteroid belt at a distance of 1.8–2.5 AU once every 3 years and 2 months (1,160 days;semi-major axis of 2.16 AU). Its orbit has aneccentricity of 0.15 and aninclination of 5° with respect to theecliptic.[2] The body'sobservation arc begins with aprecovery taken at theUccle Observatory in September 1933, nearly 57 years prior to its official discovery observation at Geisei.[1]
Okamoto is an assumedS-type asteroid,[4] the most commonspectral type in the inner asteroid belt.
Several rotationallightcurves ofOkamoto have been obtained fromphotometric observations since 2006.[7][6][8][9] Analysis of the best-rated lightcurve gave a well-definedrotation period of 2.8958 hours with a consolidated brightness amplitude between 0.11 and 0.15magnitude (U=3).[4][7]
TheCollaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – taken from8 Flora, theparent body of the Flora family – and derives a diameter of 4.59 kilometers based on anabsolute magnitude of 13.9.[4] Based on an assumed albedo of 0.14, the Johnston's archive estimates a diameter of 6.69 and 6.89 kilometer for the primary and the combined system, respectively(see below).[5]
In 2006, photometric observations obtained byDavid Higgins (E14) at Canberra, Australia,Donald Pray at Carbuncle Hill Observatory (912), as well asPeter Kušnirák andPetr Pravec atOndřejov Observatory revealed thatOkamoto is a synchronousbinary asteroid with aminor-planet moon orbiting it every 20.32 hours at an estimated average distance of13 km. The discovery was announced on 19 October 2006.[6] The mutualoccultation events indicated the presence of a satellite 25% the size of its primary, which translates into an estimated diameter of1.15–1.67 kilometers depending on the underlying size estimate of the primary.[4][5]
Thisminor planet was named after JapaneseEntomologist and elementary-school teacherHiroshi Okamoto (born 1915), who inspired the discovererTsutomu Seki with a love of the stars.[1] The official naming citation was published by theMinor Planet Center on 10 June 1998 (M.P.C. 32093).[12]
