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Discovery
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| Discovered by | Robert Luther |
| Discovery date | May 4, 1886[1] |
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Designations
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| Named after | Tyche |
| Alternate name(s) | none |
| Minor planet category |
Main belt (Eunomia family) |
| Epoch 30 January 2005 (JD 2453400.5) | |
| Aphelion | 471.289 Gm (3.15 AU) |
| Perihelion | 311.048 Gm (2.079 AU) |
| Semi-major axis | 391.168 Gm (2.615 AU) |
| Eccentricity | 0.205 |
| Orbital period | 1544.356 d (4.23 a) |
| Average orbital speed | 18.42 km/s |
| Mean anomaly | 258.968° |
| Inclination | 14.293° |
| Longitude of ascending node | 207.701° |
| Argument of perihelion | 154.948° |
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Physical characteristics
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| Dimensions | 65 km [2] |
| Mass | ~4×1017 (estimate) |
| Mean density | ~2.7 g/cm³ (estimate) [3] |
| Equatorial surface gravity | ~0.025 m/s² (estimate) |
| Escape velocity | ~0.04 km/s (estimate) |
| Rotation period | 0.417 d (10.0 h) [4][5] |
| Albedo | 0.168 [2] |
| Temperature | ~169 K max: 268 K (-5°C) |
| Spectral type | S |
| Absolute magnitude (H) | 8.5 |
258 Tyche is a relatively large main belt asteroid discovered in 1886.[1] It is classified as an S-type. Tyche orbits very close to the Eunomia family of asteroids, and could be a member based on composition. However, it is larger than all family members apart from 15 Eunomia while lying at the very edge of the family group. Hence, there is a good chance that it is an unrelated interloper.
There is some uncertainty regarding Tyche's rotation period. Various authors give values from 9.983 to 10.041 hours.[5]
It was discovered by Robert Luther on May 4, 1886 in Düsseldorf and was named after Greek goddess Tyche. Tyche's Roman equivalent is Fortuna, who also has an asteroid named after her (19 Fortuna).
This asteroids perihelion (closest approach to the Sun) is 2AU.[1]
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