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
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 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
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 ...
, 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.
See also
*
Dactyl and
Ida, another
asteroid and
asteroid moon system catalogued by astronomers
*
Florence
Florence ( ; it, Firenze ) is a city in Central Italy and the capital city of the Tuscany Regions of Italy, region. It is the most populated city in Tuscany, with 383,083 inhabitants in 2016, and over 1,520,000 in its metropolitan area.Bilan ...
, another dual-moon asteroid confirmed only in September 2017.
References
External links
Johnston Archive data14 October 1999
SwRI Press ReleaseOrbit of Petit-Prince, companion of EugeniaShape 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)
*
*
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Discoveries by Hermann Goldschmidt
Named minor planets
45 Eugenia
45 Eugenia
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