| Discovery[1] | |
|---|---|
| Discovered by | Purple Mountain Obs. |
| Discovery site | Purple Mountain Obs. |
| Discovery date | 7 December 1980 |
| Designations | |
| (3494) Purple Mountain | |
Named after | Purple Mountain Observatory[1] (Discovering observatory) |
| 1980 XW · 1962 WV1 1969 UD · 1972 OA | |
| main-belt[1][2] · (inner) Vesta[3][4] · Flora[5] | |
| Orbital characteristics[2] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 66.38yr (24,247 d) |
| Aphelion | 2.6571AU |
| Perihelion | 2.0419 AU |
| 2.3495 AU | |
| Eccentricity | 0.1309 |
| 3.60 yr (1,315 d) | |
| 237.24° | |
| 0° 16m 25.32s / day | |
| Inclination | 5.8320° |
| 234.42° | |
| 72.646° | |
| Physical characteristics | |
| 6.507±0.091 km[6][7] 7.82 km(calculated)[5] | |
| 2.928±0.001 h(1⁄2-p.)[8] 5.857±0.001 h[9] | |
| 0.24(assumed)[5] 0.347±0.035[6][7] | |
| V(SMASS-I Xu)[3] · V[4] S(assumed)[5] S/SV(SDSS-MOC)[10] | |
| 12.7[2][5][7] | |
3494 Purple Mountain, provisional designation1980 XW, is a bright Vestianasteroid and a formerlylost minor planet from the inner regions of theasteroid belt, approximately 6.5 kilometers (4 miles) in diameter. First observed in 1962, it was officially discovered on 7 December 1980, by Chinese astronomers at thePurple Mountain Observatory in Nanking, China, and later named in honor of the discovering observatory.[1] TheV-type asteroid has arotation period of 5.9 hours.[5]
Purple Mountain is a core member of theVesta family (401),[3] a giantasteroid family of typically brightV-type asteroids. Vestian asteroids have a composition akin to cumulateeucrites (HED meteorites) and are thought to have originated deep within4 Vesta's crust, possibly from theRheasilvia crater, a largeimpact crater on its southern hemisphere near the South pole, formed as a result of a subcatastrophic collision. Vesta is the main belt'ssecond-largest andsecond-most-massive body afterCeres.[11][4] 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.[5]
Purple Mountain orbits the Sun in theinner asteroid belt at a distance of 2.0–2.7 AU once every 3 years and 7 months (1,315 days;semi-major axis of 2.35 AU). Its orbit has aneccentricity of 0.13 and aninclination of 6° with respect to theecliptic.[2] The body'sobservation arc begins with aprecovery taken atPalomar Observatory in December 1951, or 29 years prior to its official discovery observation.[1]
Purple Mountain has been alost minor planet. In November 1962, Purple Mountain was observed as1962 WV1 atGoethe Link Observatory. A total of three additional observations were taken atCrimea–Nauchnij in 1969 and 1972, when it was designated as1969 UD and1972 OA, respectively, but was subsequently lost with no follow-up observations until its official discovery at Nanking in 1980.[1]
Based on the Moving Object Catalog (MOC) of theSloan Digital Sky Survey, Purple Mountain is a common, stonyS-type asteroid, with a sequential best-type taxonomy of SV.[10] TheCollaborative Asteroid Lightcurve Link (CALL) also assumes it to be a stony S-type.[5]
In the SMASS-I classification by Xu, the asteroid is aV-type. This agrees with its measured high albedo(see below) often seen among the core members of the Vesta family.[11]: 23 In 2013, a spectroscopic analysis showed it to have a composition very similar to thecumulate eucrite meteorites, which also suggests that the basaltic asteroid has originated from the crust of4 Vesta.[4]
In June 2015, a rotationallightcurve of Purple Mountain was obtained fromphotometric observations by astronomers atTexas A&M University, using the SARA-telescopes of theSoutheastern Association for Research and Astronomy consortium. The 0.9-meter SARA-North telescope is located atKitt Peak National Observatory, Arizona, while the 0.6-meter SARA-South telescope is hosted at theCerro Tololo Inter-American Observatory in Chile. Lightcurve analysis gave arotation period of 5.857 hours with a brightness variation of 0.32magnitude (U=3-).[9] One month later, in July 2015, another period of 2.928 hours and an amplitude of 0.40 magnitude was measured at MIT'sGeorge R. Wallace Jr. Observatory (U=2).[8] The results are in good agreement, apart from the fact that the latter is an alternative, monomodal solution with half the period of the former. CALL adopts the longer, bimodal period solution as the better result in its Lightcurve Data Base, due to the lightcurve's distinct amplitude and the smallphase angle of the first observation.[5]
According to the survey carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer, Purple Mountain measures 6.507 kilometers in diameter and its surface has analbedo of 0.347,[6][7] while CALL assumes an albedo of 0.24 – derived from the body's classification into the Flora family – and consequently calculates a larger diameter of 7.82 kilometers based on anabsolute magnitude of 12.7.[5]
Thisminor planet was named in honor of thePurple Mountain Observatory (PMO), an astronomical observatory located in Nanking (Nanjing), China. Built in 1934, the observatory is known for itsastrometric observations and for its numerous discoveries ofsmall Solar System bodies. It has played an important role in developing modern Chinese astronomy.[1] The official naming citation was published by theMinor Planet Center on 29 November 1993 (M.P.C. 22829).[12]
