Euphrosyne

One of the largest and most massive asteroids to be found within the Solar System's Asteroid Belt, Euphrosyne's estimated diameter of 267 km places it among the ten largest members of the belt. Nonetheless this is a dark carbonaceous asteroid orbiting in the outer reaches of the belt, and thus difficult to detect from Earth. After the detection of the first asteroid, Ceres, in 1801, more than fifty years passed before Euphrosyne was found, by astronomer James Ferguson in the year 1854. At that time it was the thirty-first asteroid to be found in the belt, a region now known to contain tens of thousands of objects.

A notable feature of Euphrosyne is its near-spherical shape, and this is related to its tumultuous history. The asteroid seems to have undergone a cataclysmic collision in the distant past, probably some three hundred million years ago. After this violent event, Euphrosyne reaccumulated under gravity, resulting in the unusually regular form it shows today. That reaccumulation left it with at least one tiny moon, an as-yet-unnamed object designated S/2019 (31) 1. Thousands of fragments of further debris were left following the same highly-inclined orbit as their parent asteroid Euphrosyne, together forming a populous group of small asteroids known as the Euphrosyne family.

Euphrosyne takes its name from Greek mythology, and specifically from one of the three Charites or Graces. These Graces have various names in different sources, but classically there were three of them, with the others being named Aglaea and Thalia. These other two Charites also have asteroids named for them: 23 Thalia was discovered in 1852, two years before Euphrosyne, and 47 Aglaja in 1857, three years afterward.