140 Siwa
Main-belt asteroid
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140 Siwa is a large and dark main-belt asteroid that was discovered by Austrian astronomer Johann Palisa on October 13, 1874. It was named after Živa (Šiwa), a Slavic goddess of fertility. This object is orbiting the Sun at a distance of 2.73 AU with an eccentricity of 0.22 and an orbital period of 4.52 years. The orbital plane is inclined at an angle of 3.2°.
Lightcurve-base 3D-model of 140 Siwa. | |
| Discovery | |
|---|---|
| Discovered by | J. Palisa |
| Discovery site | Austrian Naval Obs. |
| Discovery date | 13 October 1874 |
| Designations | |
| (140) Siwa | |
| Pronunciation | /ËÊiËwÉ/[citation needed] |
Named after | Živa |
| A874 TB; 1948 AL | |
| Main belt | |
| Orbital characteristics[1] | |
| 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° | |
| Physical characteristics | |
| Dimensions | 109.79±3.0 km |
| Mass | 1.4Ã1018 kg |
| 34.445 h (1.4352 d)[1] 34.407 h[2] | |
| 0.0676±0.004 | |
| C-type asteroid[3] | |
| 8.34 | |
A 2004 study of the spectrum of 140 Siwa matched a typical C-type asteroid with typical carbonaceous chondrite makeup. There are no absorption features of mafic minerals found.[3] The classification was later revised to a P-type asteroid.[4]
Infrared measurement yields a diameter estimate of 110 km. Attempts to measure the rotation period of 140 Siwa 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.[2]
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.[5]
