Eugenia ( minor planet designation: 45 Eugenia) is a large asteroid of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, c ...

. It is famed as one of the first asteroids to be found to have a

moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

orbiting it. It was also the second triple asteroid to be discovered, after 87 Sylvia.

Discovery

Eugenia was discovered on 27 June 1857 by the Franco-German amateur astronomer

Hermann Goldschmidt Hermann Mayer Salomon Goldschmidt (June 17, 1802 – August 30 or September 10 1866) was a German-French astronomer and painter who spent much of his life in France. He started out as a painter, but after attending a lecture by the famous Fren ...

. His instrument of discovery was a 4-inch aperture telescope located in his sixth floor apartment in the 6th Arrondissement of

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), ma ...

. It was the forty-fifth

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''mino ...

to be discovered. The preliminary

orbital element 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 ...

s were computed by Wilhelm Forster in Berlin, based on three observations in July, 1857. The asteroid was named by its discoverer after Empress Eugenia di Montijo, the wife of

Napoleon III Napoleon III (Charles Louis Napoléon Bonaparte; 20 April 18089 January 1873) was the first President of France (as Louis-Napoléon Bonaparte) from 1848 to 1852 and the last monarch of France as Emperor of the French from 1852 to 1870. A nephew ...

. It was the first asteroid to be definitely named after a real person, rather than a figure from classical legend.

Physical characteristics

Eugenia is a large asteroid, with a

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

of 214 km. It is an

F-type asteroid F-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-group. Characteristics F-type asteroids have spectra generally similar to those of the B-type asteroids, but lack the "water" absorption feature ar ...

, which means that it is very dark in colouring (darker than

soot Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...

) with a

carbonaceous Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up ...

composition. Like Mathilde, its density appears to be unusually low, indicating that it may be a loosely packed

rubble pile In astronomy, a rubble pile is a celestial body that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the ...

, not a monolithic object. Eugenia appears to be almost anhydrous. Lightcurve analysis indicates that Eugenia's pole most likely points towards

ecliptic coordinates The ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small Solar System bodi ...

(β, λ) = (-30°, 124°) with a 10° uncertainty, which gives it an

axial tilt In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orb ...

of 117°. Eugenia's rotation is then retrograde, rotating backward to its orbital plane.

Satellite system

Petit-Prince

In November 1998, astronomers at the Canada-France-Hawaii Telescope on Mauna Kea,

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

, discovered a small

orbiting Eugenia. This was the first time an asteroid moon had been discovered by a ground-based telescope. The moon is much smaller than Eugenia, about 13 km in

, and takes five days to complete an orbit around it. The discoverers chose the name "Petit-Prince" (formally "(45) Eugenia I Petit-Prince"). This name refers to Empress Eugenia's son, the Prince Imperial. However, the discoverers also intended an allusion to the children's novella ''

The Little Prince ''The Little Prince'' (french: Le Petit Prince, ) is a novella by French aristocrat, writer, and military pilot Antoine de Saint-Exupéry. It was first published in English and French in the United States by Reynal & Hitchcock in April 1943 an ...

'' by Antoine de Saint-Exupéry, which is about a young prince who lives on an asteroid.William J. Merlin et al.
"On a Permanent Name for Asteroid S/1998(45)1"
26 May 2000.

S/2004 (45) 1

A second, smaller (estimated diameter of 6 km) satellite that orbits closer to Eugenia than Petit-Prince has since been discovered and provisionally named S/2004 (45) 1. It was discovered by analyses of three images acquired in February 2004 from the 8.2 m VLT "Yepun" at the European Southern Observatory (ESO)

Cerro Paranal Cerro Paranal is a mountain in the Atacama Desert of northern Chile and is the home of the Paranal Observatory. Prior to the construction of the observatory, the summit was a horizontal control point with an elevation of ; now it is above sea ...

, in

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

. The discovery was announced in IAUC 8817, on 7 March 2007 by

Franck Marchis Franck Marchis (born April 6, 1973 in Caen, France), astronomer and planetary scientist, is best known for his discovery and characterization of multiple asteroids, his study of Io volcanism and imaging of exoplanets, planets around other stars ...

and his IMCCE collaborators. It orbits the asteroid at about ~700 km, with an orbital period of 4.7 days.

References

External links

Johnston Archive data

14 October 1999
SwRI Press Release

Orbit of Petit-Prince, companion of Eugenia

Shape model derived from lightcurve (on page 17)

14 frames of (45) Eugenia primary taken with the Keck II AO from Dec 2003 to Nov 2011
(Franck Marchis) * * {{DEFAULTSORT:Eugenia 000045 Discoveries by Hermann Goldschmidt Named minor planets 45 Eugenia 45 Eugenia 000045 000045 000045 18570627