Eugenia (minor planet designation: 45 Eugenia) is a large asteroid of the asteroid belt. It is famed as one of the first asteroids to be found to have a moon orbiting it. It is also the second known triple asteroid, after 87 Sylvia.

45 Eugenia
45 eugenia-01.jpg
CFHT time-lapse image of Eugenia and Petit-Prince, showing five stages in the moon's orbit. The 'flare' around them is an imaging artifact.
Discovered byH. Goldschmidt
Discovery date27 June 1857
MPC designation(45) Eugenia
Pronunciation/jˈniə/ yoo-JEE-nee-ə
Named after
Empress Eugénie
1941 BN
Main belt
Orbital characteristics[2]
Epoch November 26, 2005 (JD 2453701.5)
Aphelion440.305 Gm (2.943 AU)
Perihelion373.488 Gm (2.497 AU)
406.897 Gm (2.720 AU)
1638.462 d (4.49 a)
Known satellitesPetit-Prince
S/2004 (45) 1
Physical characteristics
Dimensions232 × 193 × 161 km[3]
305 × 220 × 145 km[4][5]
Mean radius
107.3 ± 2.1 km[4]
Mass(5.69 ± 0.1) ×1018 kg[3]
(5.8 ± 0.2) ×1018 kg[6][7][8]
Mean density
1.1 ± 0.1 g/cm³[3]
1.1 ± 0.3 g/cm³[7]
Equatorial surface gravity
0.017 m/s²[9]
Equatorial escape velocity
0.071 km/s[9]
0.2375 d (5.699 h)[10]


Eugenia was discovered on 27 June 1857 by the Franco-German amateur astronomer Hermann Goldschmidt.[12] His instrument of discovery was a 4-inch aperture telescope located in his sixth floor apartment in the Latin Quarter of Paris.[13] It was the forty-fifth minor planet to be discovered. The preliminary orbital elements were computed by Wilhelm Forster in Berlin, based on three observations in July, 1857.[14]

The asteroid was named by its discoverer after Empress Eugenia di Montijo, the wife of Napoleon III.[12] It was the first asteroid to be definitely named after a real person, rather than a figure from classical legend,[15] although there was some controversy about whether 12 Victoria was really named for the mythological figure or for Queen Victoria.[citation needed]

Physical characteristicsEdit

Eugenia is a large asteroid, with a diameter of 214 km. It is an F-type asteroid, which means that it is very dark in colouring (darker than soot) with a carbonaceous composition. Like Mathilde, its density appears to be unusually low, indicating that it may be a loosely packed rubble pile, not a monolithic object. Eugenia appears to be almost anhydrous.[16] Lightcurve analysis indicates that Eugenia's pole most likely points towards ecliptic coordinates (β, λ) = (-30°, 124°) with a 10° uncertainty,[5] which gives it an axial tilt of 117°. Eugenia's rotation is then retrograde, rotating backward to its orbital plane.

Satellite systemEdit


In November 1998, astronomers at the Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, discovered a small moon 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, 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 by Antoine de Saint-Exupéry, which is about a young prince who lives on an asteroid.[17]

S/2004 (45) 1Edit

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 m VLT "Yepun" at the European Southern Observatory (ESO) Cerro Paranal, in Chile.[19] The discovery was announced in IAUC 8817, on 7 March 2007 by Franck Marchis and his IMCCE collaborators. It orbits the asteroid at about ~700 km, with an orbital period of 4.7 days.[18]

In popular cultureEdit

The Asteroids Galaxy Tour (perhaps aptly) released a song titled "Theme from 45 Eugenia," which appears on their album Out of Frequency.

See alsoEdit


  1. ^ "Discovery Circumstances: Numbered Minor Planets". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. 9 February 2010. Archived from the original on 10 May 2008. Retrieved 12 August 2010.
  2. ^ "ASTORB". Orbital elements database. Lowell Observatory.
  3. ^ a b c Baer, Jim (2008). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2 July 2013. Retrieved 7 December 2008.
  4. ^ a b c d "Supplemental IRAS minor planet survey". Planetary Science Institute. Archived from the original on 17 August 2009.
  5. ^ a b c Kaasalainen, M.; et al. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus. 159 (2): 369–395. Bibcode:2002Icar..159..369K. doi:10.1006/icar.2002.6907.
  6. ^ Marchis, F. "synthesis of several observations". Berkeley. Archived from the original on 13 September 2006.
  7. ^ a b Marchis, F.; et al. (2004). "Fine Analysis of 121 Hermione, 45 Eugenia, and 90 Antiope Binary Asteroid Systems With AO Observations". Bulletin of the American Astronomical Society. 36: 1180. Bibcode:2004DPS....36.4602M.
  8. ^ Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
  9. ^ a b On the extremities of the long axis.
  10. ^ "PDS lightcurve data". Planetary Science Institute. Archived from the original on 9 April 2009.
  11. ^ "PDS node taxonomy database". Planetary Science Institute. Archived from the original on 5 August 2009.
  12. ^ a b Schmadel, Lutz D. (2003). Dictionary of minor planet names. Physics and astronomy online library (5th ed.). Springer. p. 19. ISBN 3-540-00238-3.
  13. ^ J. C. (1867). "Memoirs of the Royal Astronomical Society". Memoirs of the Royal Astronomical Society. Priestley and Weale. 36: 155. Retrieved 13 August 2010.
  14. ^ Goldschmidt, H. (July 1857). "New Planet (45)". Monthly Notices of the Royal Astronomical Society. 17: 263–264. Bibcode:1857MNRAS..17..263G. doi:10.1093/mnras/17.9.263b.
  15. ^ Tobin, William (2003). The life and science of Léon Foucault: the man who proved the earth rotates. Cambridge University Press. p. 301. ISBN 0-521-80855-3.
  16. ^ A. S. Rivkin (2002). "Calculated Water Concentrations on C Class Asteroids" (PDF). Lunar and Planetary Institute. Retrieved 22 May 2008.
  17. ^ William J. Merlin et al., "On a Permanent Name for Asteroid S/1998(45)1". May 26, 2000.
  18. ^ a b Marchis, F.; Baek, M.; Descamps, P.; Berthier, J.; Hestroffer, D.; Vachier, F. (2007). "S/2004 (45) 1". IAU Circular. 8817. Bibcode:2007IAUC.8817....1M.
  19. ^ "IMCCÉ Breaking News". Archived from the original on 27 September 2007. Retrieved 30 April 2019.

External linksEdit