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| Orbital characteristics 1 | |
|---|---|
| Orbit type | Main belt |
| Semimajor axis | 2.732 AU |
| Perihelion distance | 2.143 AU |
| Aphelion distance | 3.322 AU |
| Orbital period | 4.52 years |
| Inclination | 3.19° |
| Eccentricity | 0.216 |
| Physical characteristics | |
| Diameter 6 | 103 km |
| Mass 6 | 1.5 × 1018 kg |
| Rotation period | 18.5 hoursIn modern usage, an hour is defined as a unit of time 60 minutes, or 3600 seconds in length. It is approximately 1/24 of a median Earth day. There is also the hour of right ascension a unit of both time and angle. Earlier definitions of the hour: One twel |
| Spectral classIn astronomy the term spectral class refers to classifying objects according to their spectral lines, which indicate an object's chemical composition. It can be used to refer to the classification of: Stars Asteroids Astronomy. 5 | PP-type asteroids have low albedo and a featureless reddish spectrum. It has been suggested that they have a composition of organic rich silicates, carbon and anhydrous silicates, possibly with water ice in their interior. P-type asteroids are found in the ( CC-type asteroids are carbonaceous asteroids. They form 75% of known asteroids, and are extremely dark ( albedo 0. 03), similar to carbonaceous chondrite meteorites (types CI and CM). They dominate the outer belt beyond 2. These asteroids have approximatel 6) |
| Abs. magnitudeIn astronomy, absolute magnitude is the apparent magnitude, m an object would have if it were at a standardized distance away. It allows the overall brightnesses of objects to be compared without regards to distance. Absolute Magnitude for stars M In stel 1 | 8.34 |
| AlbedoNote: This article discusses the physical or planetological property of albedo. For other usage, see Albedo (disambiguation). The albedo is a measure of reflectivity of a surface or body. It is the ratio of electromagnetic radiation reflected to the amoun 4 | 0.067 |
| History 2 | |
| Discoverer | J. PalisaJohann Palisa ( December 6 1848 May 2 1925) was an Austrian astronomer, born in Opava, Czech Republic (then part of Austrian Empire). He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gellivara in 1923., 1874 |
140 Siwa is a large and dark main belt asteroid. It has a composition of a P (or possibly C-type) asteroid.
It was discovered by J. Palisa on October 13, 1874 and named after Siwa, the Slavic goddess of fertility.
Siwa has a very flat lightcurve, indicating a spherical body.
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.
Main Belt asteroids