258 Tyche
258 Tyche is a large asteroid in the main asteroid belt between Mars and Jupiter. It was discovered on May 4, 1886, by Robert Luther at the Düsseldorf-Bilk Observatory. It is about 65 kilometers across and is classified as a stony (S-type) object.
Tyche’s orbit around the Sun takes about 4.23 years. It travels from 2.08 AU at perihelion to 3.15 AU at aphelion, with an average distance (semi-major axis) of about 2.62 AU. The orbit is inclined about 14 degrees to the plane of the Solar System. Tyche sits near the Eunomia family of asteroids and could be a member, but it is larger than most family members except 15 Eunomia, so it might be an unrelated interloper.
The rotation period is about 10.0 hours, though published values range from roughly 9.98 to 10.04 hours. It has a geometric albedo of about 0.168, meaning it reflects a moderate amount of sunlight. Surface temperatures would range roughly from 169 K to 268 K, depending on sunlight.
The mass is estimated at about 4×10^17 kilograms, with a mean density around 2.7 g/cm³. Its absolute magnitude is 8.50, reflecting its intrinsic brightness.
Tyche is named after the Greek goddess Tyche, the goddess of fortune (the Roman equivalent is Fortuna). It remains distinct from the asteroid 19 Fortuna, which shares the same mythological name.
Overall, Tyche is a sizeable, bright main-belt asteroid with a rotation around 10 hours and a possible connection to the Eunomia family.
This page was last edited on 2 February 2026, at 07:26 (CET).