45 Eugenia


45 Eugenia
45 Eugenia VLT (2021), deconvolved.pdf
Discovered byH. Goldschmidt
Discovery date27 June 1857
(45) Eugenia
Named after
Empress Eugénie
1941 BN
Main belt
Orbital characteristics[3]
Epoch 26 November 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[4]
305 × 220 × 145 km[5][6]
Mean radius
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][10]
Mean density
1.66±0.07 g/cm3[7]
1.1±0.1 g/cm3[4]
1.1±0.3 g/cm3[9]
Equatorial surface gravity
0.017 m/s²[11]
Equatorial escape velocity
0.071 km/s[11]
0.2375 d (5.699 h)[12]
0.065 (calculated)[7]

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


Eugenia was discovered on 27 June 1857 by the Franco-German amateur astronomer Hermann Goldschmidt.[14] His instrument of discovery was a 4-inch aperture telescope located in his sixth floor apartment in the 6th Arrondissement of Paris.[15] 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.[16]

The asteroid was named by its discoverer after Empress Eugenia di Montijo, the wife of Napoleon III.[14] It was the first asteroid to be definitely named after a real person, rather than a figure from classical legend.[17]

Physical characteristics

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.[18] Lightcurve analysis indicates that Eugenia's pole most likely points towards ecliptic coordinates (β, λ) = (-30°, 124°) with a 10° uncertainty,[6] which gives it an axial tilt of 117°. Eugenia's rotation is then retrograde, rotating backward to its orbital plane.

Satellite system


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.[19]

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.[20] 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.[21] 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.[20]

See also


  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. ^ "Eugenia". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ "ASTORB". Orbital elements database. Lowell Observatory.
  4. ^ a b c Baer, Jim (2008). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2 July 2013. Retrieved 7 December 2008.
  5. ^ a b c d "Supplemental IRAS minor planet survey". Planetary Science Institute. Archived from the original on 17 August 2009.
  6. ^ 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.
  7. ^ a b c d P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
  8. ^ Marchis, F. "synthesis of several observations". Berkeley. Archived from the original on 13 September 2006.
  9. ^ 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.
  10. ^ Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
  11. ^ a b On the extremities of the long axis.
  12. ^ "PDS lightcurve data". Planetary Science Institute. Archived from the original on 9 April 2009.
  13. ^ "PDS node taxonomy database". Planetary Science Institute. Archived from the original on 5 August 2009.
  14. ^ 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.
  15. ^ J. C. (1867). "Memoirs of the Royal Astronomical Society". Memoirs of the Royal Astronomical Society. Priestley and Weale. 36: 155. Retrieved 13 August 2010.
  16. ^ 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.
  17. ^ 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.
  18. ^ A. S. Rivkin (2002). "Calculated Water Concentrations on C Class Asteroids" (PDF). Lunar and Planetary Institute. Retrieved 22 May 2008.
  19. ^ William J. Merlin et al., "On a Permanent Name for Asteroid S/1998(45)1". 26 May 2000.
  20. ^ 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.
  21. ^ "IMCCÉ Breaking News". Archived from the original on 27 September 2007. Retrieved 30 April 2019.

External links

  • Johnston Archive data
  • Astronomical Picture of Day 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)
  • 45 Eugenia at AstDyS-2, Asteroids—Dynamic Site
    • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
  • 45 Eugenia at the JPL Small-Body Database Edit this at Wikidata
    • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters