| Discovery[1] | |
|---|---|
| Discovered by | C. Shoemaker |
| Discovery site | Palomar Obs. |
| Discovery date | 24 January 1988 |
| Designations | |
| (4217) Engelhardt | |
Named after | Wolf von Engelhardt (German mineralogist)[2] |
| 1988 BO2 · 1944 RL 1951 RY1 · 1970 AA | |
| main-belt · Phocaea[3][4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 72.73 yr (26,563 days) |
| Aphelion | 2.8045AU |
| Perihelion | 1.8246 AU |
| 2.3145 AU | |
| Eccentricity | 0.2117 |
| 3.52yr (1,286 days) | |
| 272.23° | |
| 0° 16m 47.64s / day | |
| Inclination | 23.129° |
| 355.44° | |
| 348.79° | |
| Knownsatellites | 1(P: 36.03 h)[5][a] |
| Physical characteristics | |
| Dimensions | 7.34±1.36 km[6] 8.742±0.356 km[7][8] 9.16±1.0 km[9] 9.24 km(derived)[3] |
| 3.066±0.001h[10] 3.0661±0.0002 h[5][a] | |
| 0.2108±0.052[9] 0.231±0.046[7][8] 0.2489(derived)[3] 0.37±0.17[6] | |
| S[3][11] | |
| 12.10±0.67[11] · 12.20[6] · 12.3[1][3] · 12.50[7][9] | |
4217 Engelhardt, provisional designation1988 BO2, is a stony Phoceanasteroid and a potentiallybinary system from the inner regions of theasteroid belt, approximately 9 kilometers in diameter. It was discovered on 24 January 1988, by American astronomerCarolyn Shoemaker atPalomar Observatory in California, and later named after German mineralogistWolf von Engelhardt.[12]
Engelhardt is a stonyS-type asteroid and a member of thePhocaea family (701).[4] It orbits the Sun in theinner main-belt at a distance of 1.8–2.8 AU once every 3 years and 6 months (1,286 days). Its orbit has aneccentricity of 0.21 and aninclination of 23° with respect to theecliptic.[1]
It was first identified as1944 RL atTurku Observatory in 1944, extending the body'sobservation arc by 44 years prior to its official discovery observation at Palomar.[12] It will pass about 0.0017 AU (250,000 km) from Earth threatening asteroid(29075) 1950 DA in 2736.[13]
In November 2004, a rotationallightcurve ofEngelhardt was obtained from photometric observations by American astronomerBrian Warner at this Palmer Divide Observatory in Colorado.[a] Lightcurve analysis gave a well-definedrotation period of 3.066 hours with a brightness amplitude of 0.16magnitude (U=3).[10]
In December 2011, a follow-up observation by Warner gave a period of 3.0661 hours with 0.18 amplitude (U=3).[5] Due to a couple of supposed occultation and eclipsing events, Warner also suspects thatEngelhardt might by abinary system with aminor-planet moon orbiting it every 36.03 hours. The result, however, is far from conclusive.[a]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite, and NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission,Engelhardt measures between 7.34 and 9.16 kilometers in diameter and its surface has analbedo between and 0.231 and 0.37.[7] TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.2489 and a diameter of 9.24 kilometers with on anabsolute magnitude of 12.3.[3]
Baltic German geologist and mineralogistWolf von Engelhardt (1910–2008), expert onimpact craters and related mineral metamorphism. He was a professor at theUniversity of Tübingen and a longtime director of itsInstitute of Mineralogy and Petrography.[2] The approved naming citation was published by theMinor Planet Center on 27 June 1991 (M.P.C. 18456).[14]
