.png) Lightcurve-based 3D-model ofTama | |
| Discovery[1] | |
|---|---|
| Discovered by | O. Oikawa |
| Discovery site | Tokyo Astronomical Obs. |
| Discovery date | 17 November 1927 |
| Designations | |
| (1089) Tama | |
| Pronunciation | Japanese:[tama] |
Named after | Tama River[2] (Japaneseriver) |
| 1927 WB · 1930 ST 1952 HE4 · A894 VA A904 VD · A919 HA | |
| main-belt · (inner) Flora[3] · background[4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 122.40 yr (44,708 days) |
| Aphelion | 2.4951AU |
| Perihelion | 1.9327 AU |
| 2.2139 AU | |
| Eccentricity | 0.1270 |
| 3.29yr (1,203 days) | |
| 82.843° | |
| 0° 17m 57.12s / day | |
| Inclination | 3.7264° |
| 71.489° | |
| 354.29° | |
| Knownsatellites | 1 [3][5][6] |
| Physical characteristics | |
| Dimensions | 11.33±2.00 km[7] 12.2±1.6 km[8] 12.82 km(derived)[3] 12.92±0.6 km[9] 13.08±0.37 km[10] 13.082±0.373 km[10] 13.32±0.19 km[11] |
| 4(dated)h[12] 16.4±0.1 h[13] 16.44 h[8] 16.444±0.001 h[14] 16.4442±0.0004 h[6][13] 16.445±0.005 h[13] 16.45±0.05 h[13] 16.4530±0.0004 h[13] 16.464±0.004 h[15] 16.4655 h[16] | |
| 0.2048(derived)[3] 0.216±0.029[10] 0.2424±0.023[9] 0.243±0.008[11] 0.267±0.083[8] 0.32±0.23[7] | |
| S(assumed)[3] | |
| 11.60[9][11] · 11.63±0.0[8] · 11.70[7][10] · 11.8[1][3] · 11.86±0.85[17] | |
1089 Tama, provisional designation1927 WB, is an elongated Florianasteroid and synchronousbinary system from the inner regions of theasteroid belt, approximately 12 kilometers in diameter.
It was discovered by Japanese astronomerOkuro Oikawa at the old Tokyo Astronomical Observatory (389) on 17 November 1927.[18] The asteroid was named after theTama River in Japan.[2] Itsminor-planet moon was discovered in December 2003 and measures approximately 9 kilometers.[6]
Tama is a member of theFlora family (402), a giantasteroid family and the largest family of stony asteroids in the main-belt.[3] It is, however, a non-family asteroid from the main belt'sbackground population when applying the Hierarchical Clustering Method to its proper orbital elements.[4]
The asteroid orbits the Sun in theinner main-belt at a distance of 1.9–2.5 AU once every 3 years and 3 months (1,203 days). Its orbit has aneccentricity of 0.13 and aninclination of 4° with respect to theecliptic.[1]Tama was first identified asA894 VA atHeidelberg Observatory in November 1894. The body'sobservation arc begins with its identification asA904 VD at Heidelberg in November 1904, or 23 years prior to its official discovery observation at Tokyo.[18]
Tama is an assumed stonyS-type asteroid.[3]
A large number of rotationallightcurves ofTama were obtained from photometric observations since it has been identified as abinary asteroid(see below). Lightcurve analysis gave arotation period between 16.4 and 16.464 hours with a brightness variation between 0.08 and 0.41magnitude (U=2-/2-3-/3), superseding a period of 4 hours from a fragmentary lightcurve obtained in the 1990s (U=1).[6][8][12][13][15]
Tama appears to be somewhat elongated in shape.[6] LCDB's consolidated result gives a period of 16.44 hours and an amplitude of 0.41 magnitude (U=3).[3]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite, theSpitzer Space Telescope and theNEOWISE mission of theWide-field Infrared Survey Explorer,Tama measures between 11.33 and 13.32 kilometers in diameter and its surface has analbedo between 0.216 and 0.32.[7][8][9][10][11]
TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.2048 and a diameter of 12.82 kilometers based on anabsolute magnitude of 11.8.[3]
In 2004, it was announced thatTama has aminor-planet moon. The satellite was identified based on lightcurve observations with mutualoccultation and eclipsing events from 24 December 2003 to 5 January 2004 byRaoul Behrend,René Roy,Claudine Rinner,Pierre Antonini,Petr Pravec,Alan Harris,Stefano Sposetti, Russell Durkee, andAlain Klotz.[6][13] The moon measures approximately 9 kilometers in diameter. It may orbits 20 km away in a period of 16.4442 hours (synchronously).[3][5][6]
Tamas lightcurve has also been modeled. In 2013, modelling by an international study using photometric data from theUS Naval Observatory, the Uppsala Asteroid Photometric Catalogue (UAPC) and thePalmer Divide Observatory, gave a concurring rotation period of 16.4655 hours.[16] Another modeled lightcurve using data from UAPC, thePalomar Transient Factory survey, and individual observers, gave a period of 16.4461 hours as well as twospin axes of (193.0°, 32.0°) and (9.0°, 28.0°) inecliptic coordinates (λ, β).[19]
Thisminor planet was named afterTama River near the discovering Tokyo Astronomical Observatory (389) in Japan. The official naming citation was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 103).[2]
