31 Euphrosyne is one of the

largest asteroids The following is a collection of lists of asteroids of the Solar System that are exceptional in some way, such as their size or orbit. For the purposes of this article, "asteroid" refers to minor planets out to the orbit of Neptune, and includes ...

(approximately tied for 7th place, to within measurement uncertainties). It was discovered by

James Ferguson James Ferguson may refer to: Entertainment * Jim Ferguson (born 1948), American jazz and classical guitarist * Jim Ferguson, American guitarist, past member of Lotion (band), Lotion * Jim Ferguson, American movie critic, Board of Directors member ...

on September 1, 1854, the first asteroid found from North America. It is named after

Euphrosyne In ancient Greek religion and mythology, Euphrosyne (; ) is a goddess, one of the three Charites. She was sometimes named Euthymia () or Eutychia (). Family According to Hesiod, Euphrosyne and her sisters Thalia and Aglaea are the daughters ...

, one of the

Charites In Greek mythology, the Charites (; ), singular Charis (), also called the Graces, are goddesses who personify beauty and grace. According to Hesiod, the Charites were Aglaia (Grace), Aglaea, Euphrosyne, and Thalia (Grace), Thalia, who were the ...

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

. In 2019 a small companion was discovered. It is the third-roundest known asteroid (after

1 Ceres Ceres ( minor-planet designation: 1 Ceres) is a dwarf planet in the middle main asteroid belt between the orbits of Mars and Jupiter. It was the first known asteroid, discovered on 1 January 1801 by Giuseppe Piazzi at Palermo Astronomical O ...

and

10 Hygiea 10 Hygiea is a large asteroid located in the outer main asteroid belt between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observa ...

); this is thought to be due to having re-accreted after being disrupted by a collision, and it is not close to hydrostatic equilibrium.

Observations

Euphrosyne is a fairly dark body near the belt's outer edge. Consequently, it is never visible with binoculars, having a maximum

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

at the best possible opposition of around +10.2 (as in November 2011), which is fainter than any of the thirty asteroids previously discovered. Euphrosyne has a high

orbital inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth ...

and eccentricity having nodes near perihelion and aphelion, Euphrosyne's perihelion lies at the northernmost point of its orbit. During perihelic oppositions, Euphrosyne is very high in the sky from northern latitudes and invisible from southern countries such as New Zealand and Chile.

Surface

Euphrosyne is a

C-type asteroid C-type (carbonaceous ) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

with a primitive surface possibly covered by thick ejecta blanket from the collision that created its moon and collisional family. There are no deep basins. Any craters larger than 40 km in diameter must have flat floors to not be visible in the VLT images, consistent with an icy C-type composition. The lack of craters could also be due to the young age of the surface.

Mass and density

The discovery of its satellite enabled the first accurate measure of Euphrosyne's mass in 2020, at , and thus a density of . The low density suggests that Euphrosyne is half water ice if internal porosity is 20%.

Family

Euphrosyne is the namesake of a complex

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of about two thousand asteroids that share similar spectral properties and

orbital elements Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit. There are many different ways to mathematically describe the same o ...

. They are thought to have arisen from a recent collision approximately 280 million years ago. All members have relatively high orbital inclinations. The second largest body in this group, 895 Helio, is most likely an interloper.

Satellite

In 2019 a small satellite was discovered, likely resulting from the same collisional event that created the family. Preliminary orbit computations indicated an orbital period of approximately 1.2 days and a semi-major axis of 670 km. VLT images indicate that the moon is 4 km in diameter, assuming it has the same albedo as Euphrosyne.

Gallery

PIA19645-Asteroid-Euphrosyne-NEOWISE-20100517

Notes

References

External links

* * {{DEFAULTSORT:Euphrosyne 000031 Discoveries by James Ferguson (American astronomer) Named minor planets 000031 000031 000031 18540901