258 Tyche

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258 Tyche
258Tyche (Lightcurve Inversion).png
A three-dimensional model of 258 Tyche based on its light curve.
Discovered by Robert Luther
Discovery date May 4, 1886[1]
Named after
Main belt (Eunomia family)
Orbital characteristics
Epoch 30 January 2005 (JD 2453400.5)
Aphelion 471.289 Gm (3.15 AU)
Perihelion 311.048 Gm (2.079 AU)
391.168 Gm (2.615 AU)
Eccentricity 0.205
1544.356 d (4.23 a)
18.42 km/s
Inclination 14.293°
Physical characteristics
Dimensions 65 km [2]
Mass ~4×1017 (estimate)
Mean density
~2.7 g/cm³ (estimate) [3]
~0.025 m/s² (estimate)
~0.04 km/s (estimate)
0.417 d (10.0 h) [4][5]
Albedo 0.168 [2]
Temperature ~169 K
max: 268 K (-5°C)
Spectral type

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]


  1. ^ a b c "JPL Small-Body Database Browser: 258 Tyche" (2011-04-01 last obs). Retrieved 2011-08-11. 
  2. ^ a b Supplemental IRAS Minor Planet Survey
  3. ^ G. A. Krasinsky et al. Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).
  4. ^ PDS lightcurve data
  5. ^ a b D. Riccioli, C. Blanco, & M. Cigna Rotational periods of asteroids II, Planetary and Space Science, Vol. 49,, p. 657 (2001).

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