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45 Eugenia

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Discovery[1]
Discovered by H. Goldschmidt
Discovery date 27 June 1857
Designations
Pronunciation /juːˈdʒiːniə/[2]
Named after Empress Eugénie
Alternative designations 1941 BN
Minor planet category Main belt
Adjectives Eugenian
Orbital characteristics[3]
Epoch 26 November 2005 (JD 2453701.5)
Aphelion 440.305 million km (2.943 AU)
Perihelion 373.488 million km (2.497 AU)
Semi-major axis 406.897 million km (2.720 AU)
Eccentricity 0.082
Orbital period (sidereal) 1,638.462 d (4.49 a)
Mean anomaly 45.254°
Inclination 6.610°
Longitude of ascending node 147.939°
Argument of perihelion 85.137°
Known satellites Petit-Prince
S/2004 (45) 1
Physical characteristics
Dimensions 232 × 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]
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[10]
Equatorial escape velocity 0.071 km/s[10]
Sidereal rotation period 0.2375 d (5.699 h)[11]
Axial tilt 117±10°
Pole ecliptic longitude 124±10°
Pole ecliptic latitude −30±10°[6]
Geometric albedo 0.065 (calculated)[7]
0.040±0.002[5]
Spectral type F[12]
Absolute magnitude (H) 7.46[5]

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.

Discovery

Eugenia was discovered on 27 June 1857 by the Franco–German amateur astronomer Hermann Goldschmidt.[13] His instrument of discovery was a four-inch aperture telescope located in his sixth-floor apartment in the 6th arrondissement of Paris.[14] It was the 45th minor planet to be discovered. The preliminary orbital elements were computed by Wilhelm Forster in Berlin, based on three observations in July 1857.[15]

The asteroid was named by its discoverer after Empress Eugénie de Montijo, the wife of Napoleon III.[13] It was the first asteroid to be definitely named after a real person, rather than a figure from classical legend.[16]

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.[17] Lightcurve analysis indicates that Eugenia's pole most likely points towards ecliptic coordinates (β, λ) = (−30°, 124°) with a 10-degree uncertainty,[6] which gives it an axial tilt 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, 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" (or to disambiguate, "(45) Eugenia I Petit-Prince"). The name refers to Empress Eugénie's son, Prince Imperial Louis-Napoléon. 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.[18]

S/2004 (45) 1

A second, smaller (estimated diameter of 6 km) satellite that orbits closer to Eugenia than does Petit-Prince was discovered in 2004. It is provisionally named S/2004 (45) 1[19] and is informally dubbed "Petite-Princesse". 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.[20] The discovery was announced in IAUC 8817, on 7 March 2007 by Franck Marchis and his IMCCE collaborators.[19]

Moons
Name Semi-major axis Diameter Eccentricity Inclination Period
S/2004 (45) 1
(Petite-Princesse) 		610 km 6 km 0.11 ± 0.02 1.793d
Petit-Prince 1,164 km 13 km 0.002 8.0° 4.716d

See also

References

  1. Back to citation "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. Back to citation "Eugenia". Oxford English Dictionary (online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. Back to citation "ASTORB". Orbital elements database. Lowell Observatory.
  4. Back to citation occurrence 4.0 Back to citation occurrence 4.1 Back to citation occurrence 4.2 Baer, Jim (2008). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2 July 2013. Retrieved 7 December 2008.
  5. Back to citation occurrence 5.0 Back to citation occurrence 5.1 Back to citation occurrence 5.2 Back to citation occurrence 5.3 "Supplemental IRAS minor planet survey". Planetary Science Institute. Archived from the original on 17 August 2009.
  6. Back to citation occurrence 6.0 Back to citation occurrence 6.1 Back to citation occurrence 6.2 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. Back to citation occurrence 7.0 Back to citation occurrence 7.1 Back to citation occurrence 7.2 Back to citation occurrence 7.3 P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
  8. Back to citation Marchis, F. "synthesis of several observations". Berkeley. Archived from the original on 13 September 2006; 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; Uncertainty calculated from uncertainties in the orbit of Petit-Prince
  9. Back to citation 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. Back to citation occurrence 10.0 Back to citation occurrence 10.1 On the extremities of the long axis
  11. Back to citation "PDS lightcurve data". Planetary Science Institute. Archived from the original on 9 April 2009.
  12. Back to citation "PDS node taxonomy database". Planetary Science Institute. Archived from the original on 5 August 2009.
  13. Back to citation occurrence 13.0 Back to citation occurrence 13.1 Schmadel, Lutz D. (2003). Dictionary of minor planet names. Physics and astronomy online library (5th ed.). Springer. p. 19. ISBN 3-540-00238-3.
  14. Back to citation J. C. (1867). "Obituary: Herman Goldschmidt". Memoirs of the Royal Astronomical Society. 36: 114–117. Retrieved 13 August 2010.
  15. Back to citation 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.
  16. Back to citation 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.
  17. Back to citation Rivkin, A. S. (2002). "Calculated Water Concentrations on C Class Asteroids" (PDF). Lunar and Planetary Institute. Retrieved 21 July 2025.
  18. Back to citation William J. Merlin et al., "On a Permanent Name for Asteroid S/1998(45)1". 26 May 2000.
  19. Back to citation occurrence 19.0 Back to citation occurrence 19.1 Marchis, F.; Baek, M; Descamps, P; Berthier, J; Hestroffer, D; Vachier, F. (2007). "S/2004 (45) 1". IAU Circular (8817): 1. Bibcode:2007IAUC.8817....1M.
  20. Back to citation "IMCCÉ Breaking News". Archived from the original on 27 September 2007. Retrieved 30 April 2019.
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