140 Siwa
| Discovery | |
|---|---|
| Discovered by | Johann Palisa |
| Discovery date | 13 October 1874 |
| Designations | |
| MPC designation | (140) Siwa |
| Main belt | |
| Orbital characteristics | |
| Epoch 31 July 2016 (JD 2457600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 139.10 yr (50805 d) |
| Aphelion | 3.3224 AU (497.02 Gm) |
| Perihelion | 2.14323 AU (320.623 Gm) |
| 2.73283 AU (408.826 Gm) | |
| Eccentricity | 0.21575 |
| 4.52 yr (1650.1 d) | |
|
Average orbital speed
|
17.80 km/s |
| 200.674° | |
| 0° 13m 5.398s / day | |
| Inclination | 3.1860° |
| 107.263° | |
| 196.711° | |
| Earth MOID | 1.12782 AU (168.719 Gm) |
| Jupiter MOID | 1.9186 AU (287.02 Gm) |
| Jupiter Tisserand parameter | 3.317 |
| Physical characteristics | |
| Dimensions | 109.79±3.0 km |
| Mass | 1.4×1018 kg |
|
Equatorial surface gravity
|
0.0307 m/s² |
|
Equatorial escape velocity
|
0.0580 km/s |
| 34.445 h (1.4352 d) 34.407 h |
|
| 0.0676±0.004 | |
| Temperature | ~168 K |
| C-type asteroid | |
| 8.34 | |
140 Siwa /ˈʃiːwə/ is a large and dark main-belt asteroid that was discovered by Austrian astronomer Johann Palisa on October 13, 1874, and named after Šiwa, the Slavic goddess of fertility.
The Rosetta comet probe was to visit Siwa on its way to comet 46P/Wirtanen in July, 2008. However, the mission was rerouted to comet 67P/Churyumov-Gerasimenko and the flyby had to be abandoned.
Attempts to measure the rotation period of this asteroid have produced inconsistent results ranging from 14.7 to 32 hours. Photometric observations of this asteroid at the Organ Mesa Observatory in Las Cruces, New Mexico during 2010 gave an irregular light curve with a period of 34.407 ± 0.002 hours and a brightness variation of 0.05 ± 0.01 in magnitude.
A 2004 study of the spectrum matched a typical C-type asteroid with typical carbonaceous chondrite makeup. There are no absorption features of mafic minerals found. The classification was later revised to a P-type asteroid.
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