_Postrema.png) Shape model ofPostrema from itslightcurve | |
| Discovery[1] | |
|---|---|
| Discovered by | G. Neujmin |
| Discovery site | Simeiz Obs. |
| Discovery date | 29 April 1938 |
| Designations | |
| (1484) Postrema | |
| Pronunciation | /pɒˈstriːmə/ |
Named after | postrēma[2] ("the last of a group") |
| 1938 HC · 1933 DH A911 KC | |
| main-belt · (middle) Postrema[3] | |
| Adjectives | Postremian |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 84.61 yr (30,903 days) |
| Aphelion | 3.2973AU |
| Perihelion | 2.1816 AU |
| 2.7394 AU | |
| Eccentricity | 0.2036 |
| 4.53yr (1,656 days) | |
| 194.22° | |
| 0° 13m 2.64s / day | |
| Inclination | 17.300° |
| 72.767° | |
| 126.82° | |
| Physical characteristics | |
| Dimensions | 34.696±1.954 km[4] 38.82±6.78 km[5] 40.871±0.279 km[6] 41±4 km[7] 41.1±8.2 km[8] 41.73±12.60 km[9] 43.18±1.0 km[10] 43.42 km(derived)[11] 47.00±0.62 km[12] |
| 12.18978±0.00001h[13] 12.19±0.02 h[14] 12.1923±0.0005 h[15] | |
| 0.0137±0.001[10] 0.015±0.009[6] 0.035±0.001[12] 0.0367±0.0074[4] 0.0409(derived)[11] 0.05±0.01[7] 0.05±0.02[8][5] 0.05±0.04[9] | |
| SMASS =B[1][11] | |
| 10.80[7][8][9] · 10.88[5] · 10.90[1][11][12] · 12.10[4][10] | |
1484 Postrema, provisional designation1938 HC, is a carbonaceous Postremianasteroid and namesake of thePostrema family from the central regions of theasteroid belt, approximately 41 kilometers in diameter. It was discovered on 29 April 1938, by Soviet astronomerGrigory Neujmin at theSimeiz Observatory on the Crimean peninsula.[16] The name "Postrema" celebrates the astronomer's last minor planet discovery.[2]
Postrema is the parent body and namesake of thePostrema family (541),[3] a mid-sized centralasteroid family of little more than 100 members.[17]: 23
It orbits the Sun in thecentral main-belt at a distance of 2.2–3.3 AU once every 4 years and 6 months (1,656 days). Its orbit has aneccentricity of 0.20 and aninclination of 17° with respect to theecliptic.[1]
The asteroid was first identified asA911 KC atJohannesburg Observatory in May 1911. The body'sobservation arc begins with its identification as1933 DH atLowell Observatory in February 1933, more than 5 years prior to its official discovery observation at Simeiz.[16]
In theSMASS classification,Postrema is a bright carbonaceousB-type asteroid,[1] while the overallspectral type of thePostrema family has been described as that ofC- andX-type.[17]: 23
In May 2006, two rotationallightcurves ofPostrema were independently obtained from photometric observations. Lightcurve analysis gave arotation period of 12.19 and 12.1923 hours with a brightness amplitude of 0.23 and 0.22magnitude, respectively (U=2+/3-).[14][15]
The asteroids lightcurve has also been modeled, using photometric data from the Lowell Photometric Database and other sources. Modelling gave a concurring period of 12.18978 hours, as well as two spin axis of (19.0°, 44°) and (250.0°, 64°) inecliptic coordinates (λ, β).[13]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite and theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer,Postrema measures between 34.696 and 47.00 kilometers in diameter and its surface has a notably lowalbedo between 0.0137 and 0.05.[4][5][6][7][8][9][10][12]
TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.0409 and a diameter of 43.42 kilometers based on anabsolute magnitude of 10.9.[11]
Thisminor planet was named "Postrema", which means "the last of a group". It celebratesGrigory Neujmin's last numbered minor planet discovery. The officialnaming citation was published by theMinor Planet Center in June 1955 (M.P.C. 1252).[18]
The citation only holds true at the time of publication. In retrospect,Postrema is not Neujmin's last discovery, neither by number nor by its discovery date. These would be the asteroids4420 Alandreev (highest numbered) and2536 Kozyrev, officially discovered on 15 August 1939, more than a year afterPostrema.[2]
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