 | |
| Discovery[1] | |
|---|---|
| Discovered by | H. Goldschmidt |
| Discovery date | 27 June 1857 |
| Designations | |
| (45) Eugenia | |
| Pronunciation | /juːˈdʒiːniə/[2] |
Named after | Empress Eugénie |
| 1941 BN | |
| Main belt | |
| Adjectives | Eugenian |
| Orbital characteristics[3] | |
| Epoch 26 November 2005 (JD 2453701.5) | |
| Aphelion | 440.305 Gm (2.943 AU) |
| Perihelion | 373.488 Gm (2.497 AU) |
| 406.897 Gm (2.720AU) | |
| Eccentricity | 0.082 |
| 1,638.462 d (4.49a) | |
| 45.254° | |
| Inclination | 6.610° |
| 147.939° | |
| 85.137° | |
| Knownsatellites | Petit-Prince S/2004 (45) 1 |
| Physical characteristics | |
| Dimensions | 232 × 193 × 161 km[4] 305 × 220 × 145 km[5][6] |
| 94±1 km[7] 107.3±2.1 km[5] | |
| Mass | (5.8±0.1)×1018 kg[7] (5.69±0.1)×1018 kg[4] (5.8±0.2)×1018 kg[8][9][a] |
Meandensity | 1.66±0.07 g/cm3[7] 1.1±0.1 g/cm3[4] 1.1±0.3 g/cm3[9] |
Equatorialsurface gravity | 0.017 m/s2[b] |
Equatorialescape velocity | 0.071 km/s[b] |
| 0.2375 d (5.699 h)[10] | |
| 117±10° | |
| 124±10° | |
| −30±10°[6] | |
| 0.065 (calculated)[7] 0.040±0.002[5] | |
| F[11] | |
| 7.46[5] | |
45 Eugenia is a largeasteroid of theasteroid belt. It is famed as one of the first asteroids to be found to have amoon orbiting it. It was also the second triple asteroid to be discovered, after87 Sylvia.
Eugenia was discovered on 27 June 1857 by the Franco–German amateur astronomerHermann Goldschmidt.[12] His instrument of discovery was a 4-inch aperture telescope located in his sixth floor apartment in the6th arrondissement of Paris.[13] It was the 45thminor planet to be discovered. The preliminaryorbital elements were computed byWilhelm Forster in Berlin, based on three observations in July, 1857.[14]
The asteroid was named by its discoverer afterEmpress Eugénie de Montijo, the wife ofNapoleon III.[12] It was the first asteroid to be definitely named after a real person, rather than a figure from classical legend.[15]
Eugenia is a large asteroid, with adiameter of 214 km. It is anF-type asteroid, which means that it is very dark in colouring (darker thansoot) with acarbonaceous composition. LikeMathilde, its density appears to be unusually low, indicating that it may be a loosely packedrubble pile, not a monolithic object. Eugenia appears to be almostanhydrous.[16] Lightcurve analysis indicates that Eugenia's pole most likely points towardsecliptic coordinates (β, λ) = (−30°, 124°) with a 10-degree uncertainty,[6] which gives it anaxial tilt of 117°. Eugenia's rotation is thenretrograde, rotating backward to its orbital plane.
In November 1998, astronomers at theCanada–France–Hawaii Telescope onMauna Kea,Hawaii, discovered a smallmoon orbiting Eugenia. This was the first time anasteroid moon had been discovered by a ground-based telescope. The moon is much smaller than Eugenia, about 13 km indiameter, 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, thePrince Imperial. However, the discoverers also intended an allusion to the children'snovellaThe Little Prince byAntoine de Saint-Exupéry, which is about a young prince who lives on an asteroid.[17]
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.[18] It was discovered by analyses of three images acquired in February 2004 from the 8.2 mVLT "Yepun" at theEuropean Southern Observatory (ESO)Cerro Paranal, inChile.[19] The discovery was announced in IAUC 8817, on 7 March 2007 byFranck Marchis and hisIMCCE collaborators. It orbits the asteroid at about ~700 km, with an orbital period of 4.7 days.[18]
