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Wednesday 18 January 2012

11th Largest Asteroid, 31 Euphrosyne

31 Euphrosyne is one of the largest main-belt asteroids and the 11th largest overall currently know. Euphrosyne was the first asteroid found from North America.

Discovery

Euphrosyne was discovered by James Ferguson on September 1, 1854.

Naming

Euphrosyne the asteroid is named after Euphrosyne, one of the Charites in Greek mythology.

In Greek mythology, Euphrosyne was one of the Charites, known in English also as the "Three Graces". She is also the Goddess of Joy, a daughter of Zeus and Eurynome, and the incarnation of grace and beauty. Also known as the goddess of Mirth.

Stats

Diameter (mean): 256 km
Semi-major axis: 3.155 AU
Orbital Period: 5.60 years
Rotation period: 5.53 hrs
Date discovered: 1854.9.1
Class: C
Type: Outer Main-belt Asteroid
(data from JPL Small-Body Database)

Orbit

Euphrosyne orbits near the asteroid belt's outer edge. Consequently Euphrosyne is never visible with binoculars, having a maximum magnitude at the best possible opposition of around +10.2, which is actually fainter than any of the thirty asteroids discovered before it.

Euphrosyne's orbit is also quite unusual and bears a considerable resemblance to that of 2 Pallas in its high inclination and eccentricity.

Whereas Pallas and Eris - the only larger bodies with comparably tilted orbits - have nodes near perihelion and aphelion, Euphrosyne's perihelion lies at the northernmost point of its orbit.

Physical Characteristics

Euphrosyne is a very little-studied body despite being one of the largest asteroids. It is a C-type asteroid with a primitive surface and has fairly dark body.

The mass estimate of Euphrosyne in Baer (2011) makes it apparently the 5th-most-massive asteroid, coming after only the big four. It also has the highest estimated density, indicating that it is a solid body like the other largest asteroids.

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