| Discovery[1] | |
|---|---|
| Discovered by | R. H. McNaught |
| Discovery site | Siding Spring Obs. |
| Discovery date | 20 September 1990 |
| Designations | |
| (5645) 1990 SP | |
| 1990 SP | |
| Apollo · NEO[2] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 40.89 yr (14,935 days) |
| Aphelion | 1.8798AU |
| Perihelion | 0.8302 AU |
| 1.3550 AU | |
| Eccentricity | 0.3873 |
| 1.58yr (576 days) | |
| 339.42° | |
| 0° 37m 29.64s / day | |
| Inclination | 13.507° |
| 45.762° | |
| 48.178° | |
| Earth MOID | 0.0537 AU |
| Physical characteristics | |
| Dimensions | 1.648 km[3] 1.65 km(taken)[4] 1.668±0.018 km[5][6] 1.849±0.334 km[7] 2.20±0.74 km[8] |
| 30.39±0.04h[9] | |
| 0.06±0.08[10] 0.062±0.079[8] 0.068±0.032[7] 0.0827[3] 0.121±0.022[5][6] | |
| P[10] · CXT[11] · S[4] | |
| 16.75±0.2(R)[9] · 16.8[5] · 17.1[1] · 17.20±0.3[7] · 17.24±0.206[3][4] | |
(5645) 1990 SP is an eccentric and tumblingasteroid, classified asnear-Earth object of theApollo group, approximately 1.7 kilometers in diameter. It was discovered on 20 September 1990, by Scottish–Australian astronomerRobert McNaught at theSiding Spring Observatory in Canberra, Australia.[2] Scientists have said that it has a '1 in 364 billion chance' of colliding with theEarth.
The asteroid orbits the Sun at a distance of 0.8–1.9 AU once every 1 years and 7 months (576 days). Its orbit has aneccentricity of 0.39 and aninclination of 14° with respect to theecliptic.[1]
This near-Earth asteroid has an Earthminimum orbit intersection distance of 0.055 AU (8,200,000 km), only slightly above the threshold minimum distance of 19.5lunar distances (0.05 AU) to make it apotentially hazardous object. It also makes close approaches to Mars. On 14 April 1969, it passed the Red Planet at only 0.013 AU (1,900,000 km).[1]
Published by theDigitized Sky Survey (DSS), a firstprecovery was taken at the discovering observatory in 1974, extending the asteroid'sobservation arc by 16 years prior to its discovery.[2]
The stonyS-type asteroid is also characterized as aP-type, based on post-cryogenic observations by theSpitzer Space Telescope,[10] while observations at theNASA Infrared Telescope Facility using itsSpeX instrument during a follow-up campaign of the Spitzer-observed objects between 2009 and 2012, gave it a C/X/T spectral type.[11]
In April 2002, Czech astronomerPetr Pravec obtained a rotationallightcurve from a photometric observations, which gave a relatively longperiod of30.39±0.04 hours with a brightness variation of 0.7 inmagnitude (U=2). The observations have also shown that the body is most likely in a tumbling motion.[4][9]
Estimates for the body's diameter range from 1.6 to 2.2 kilometers with analbedo for its surface between 0.06 and 0.12, according to observations made by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer and by the Spitzer Space Telescope.[3][5][6][7][8] TheCollaborative Asteroid Lightcurve Link takes the revised WISE data – an albedo of 0.0872 and a diameter of 1.65 kilometers – as the best of all available results.[3][4]
