641 Agnes
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| Discovery[1] | |
|---|---|
| Discovered by | M. F. Wolf |
| Discovery site | Heidelberg Obs. |
| Discovery date | 8 September 1907 |
| Designations | |
| (641) Agnes | |
| Pronunciation | /ˈæɡnɪs/,[citation needed] German: [ˈaːɡnɛs, ˈaŋnəs][2] |
Named after | unknown[3] |
| 1907 ZX · 1952 FD1 | |
| main-belt · Flora[4] | |
| Orbital characteristics[1] | |
| Epoch 16 February 2017 (JD 2457800.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 109.38 yr (39,951 days) |
| Aphelion | 2.5055 AU |
| Perihelion | 1.9346 AU |
| 2.2200 AU | |
| Eccentricity | 0.1286 |
| 3.31 yr (1,208 days) | |
| 335.75° | |
| 0° 17m 52.8s / day | |
| Inclination | 1.7119° |
| 41.020° | |
| 17.704° | |
| Physical characteristics | |
| Dimensions | 8.26±1.42 km[5] 8.81 km (calculated)[4] 9±2 km[6] 9.24±0.64 km[7] 9.446±0.166 km[8] 9.74±2.66 km[9] |
| 8.9 h[10] 178.0±0.1 h[6] | |
| 0.20±0.07[4][6] 0.21±0.15[9] 0.217±0.043[8] 0.299±0.044[7] 0.30±0.11[5] | |
| V–R = 0.500±0.050[6] S[4][11] | |
| 12.10[7] · 12.40[5][8] · 12.5[1] · 12.61[9] · 12.64±0.05[4][6] · 12.72±0.16[11] | |
641 Agnes, provisional designation 1907 ZX, is a stony Florian asteroid and slow rotator from the inner regions of the asteroid belt, approximately 9 kilometers (6 mi) in diameter.
It was discovered on 8 September 1907, by German astronomer Max Wolf at Heidelberg Observatory in southern Germany.[12] The meaning of the asteroids's name is unknown.[3]
Agnes is a stony S-type asteroid and a member of the Flora family, one of the largest groups of stony asteroids in the asteroid belt. It orbits the Sun in the inner main-belt at a distance of 1.9–2.5 AU once every 3 years and 4 months (1,208 days). Its orbit has an eccentricity of 0.13 and an inclination of 2° with respect to the ecliptic.[1] The body's observation arc begins with a recovered observation at Vienna Observatory, one month after its official discovery observation at Heidelberg.[12]
Physical characteristics
Rotation period
In March 1975, photometric observations by Swedish astronomer Claes-Ingvar Lagerkvist measured a period of 8.9 hours for Agnes. The lightcurve, however, was fragmentary and the result uncertain (U=1).[4][10]
In October 2013, the first reliable rotational lightcurve of Agnes was obtained by astronomers Frederick Pilcher, Lorenzo Franco and Luis Martinez at Organ Mesa (G50) and Balzaretto Observatory (A81) respectively. Lightcurve analysis gave a well-defined rotation period of 178.0 hours with a brightness variation of 0.55 magnitude (U=3). The team also assumed a standard albedo for stony S-type asteroids of 0.20, calculated an absolute magnitude of 12.64, estimated a mean diameter of 9±2 kilometers, and measured a V–R color index of 0.50.[6]
With such a long rotation period, Agnes is a slow rotator, of which a few hundred minor planets are currently known.
Diameter and albedo
According to the surveys carried out by the Japanese Akari satellite and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Agnes measures between 8.26 and 9.74 kilometers (5.13 and 6.05 mi) in diameter, and its surface has an albedo between 0.21 and 0.30.[5][7][8][9] The Collaborative Asteroid Lightcurve Link adopts the results obtained by Pilcher,[6] and calculates a diameter of 8.81 kilometers.[4]
