258 Tyche

Minor Planet | name=258 Tyche
discoverer=Robert Luther
discovery_date=May 4, 1886
designations="none"
category=Main belt (Eunomia family)
epoch=30 January, 2005 (JD 2453400.5)
semimajor=391.168 Gm (2.615 AU)
perihelion=311.048 Gm (2.079 AU)
aphelion=471.289 Gm (3.15 AU)
eccentricity=0.205
period=1544.356 d (4.23 a)
inclination=14.293°
asc_node=207.701°
arg_peri=154.948°
mean_anomaly=258.968°
speed=18.42 km/s
dimensions=65 km [http://www.psi.edu/pds/archive/astdata04/simps04/diamalb.tab Supplemental IRAS Minor Planet Survey] ]
mass=~4×10¹⁷ "(estimate)"
density=~2.7 g/cm³ "(estimate)" G. A. Krasinsky et al "Hidden Mass in the Asteroid Belt", Icarus, Vol. 158, p. 98 (2002).]
gravity=~0.025 m/s² "(estimate)"
escape_velocity=~0.04 km/s "(estimate)"
rotation=0.417 d (10.0 h) [http://www.psi.edu/pds/archive/lc.html PDS lightcurve data] ] D. Riccioli, C. Blanco, & M. Cigna " [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001P%26SS...49..657R&db_key=AST&data_type=HTML&format=&high=444b66a47d18789 Rotational periods of asteroids II] ", Planetary and Space Science, Vol. 49,, p. 657 (2001).]
spectral_class=S
abs_mag=8.5
albedo=0.168
temperature=~169 K
"max:" 268 K (-5°C)

258 Tyche is a relatively large Main belt asteroid. 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.

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).

References

* [ftp://ftp.lowell.edu/pub/elgb/astorb.html The Asteroid Orbital Elements Database]
* [http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html Minor Planet Discovery Circumstances]
* [http://spiff.rit.edu/richmond/parallax/phot/LCSUMPUB.TXT Asteroid Lightcurve Data File]