Astronomy:45 Eugenia

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45 Eugenia
VLT-SPHERE image of Eugenia
Discovery[1]
Discovered byH. Goldschmidt
Discovery date27 June 1857
Designations
(45) Eugenia
Pronunciation/juːˈdʒiːniə/[2]
Named afterEmpress Eugénie
1941 BN
Minor planet categoryMain belt
AdjectivesEugenian
Orbital characteristics[3]
Epoch 26 November 2005 (JD 2453701.5)
|{{{apsis}}}|helion}}440.305 million km (2.943 AU)
|{{{apsis}}}|helion}}373.488 million km (2.497 AU)
406.897 million km (2.720 AU)
Eccentricity0.082
Orbital period1,638.462 d (4.49 a)
Mean anomaly45.254°
Inclination6.610°
Longitude of ascending node147.939°
85.137°
Known satellitesPetit-Prince
S/2004 (45) 1
Physical characteristics
Dimensions232 × 193 × 161 km[4]
305 × 220 × 145 km[5][6]
Mean radius94±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][lower-alpha 1]
Mean density1.66±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[lower-alpha 2]
Equatorial escape velocity
0.071 km/s[lower-alpha 2]
Sidereal rotation period0.2375 d (5.699 h)[10]
Axial tilt117±10°
Pole ecliptic latitude−30±10°[6]
Pole ecliptic longitude124±10°
Geometric albedo0.065 (calculated)[7]
0.040±0.002[5]
F[11]
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.[12] His instrument of discovery was a four-inch aperture telescope located in his sixth-floor apartment in the 6th arrondissement of Paris.[13] 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.[14]

The asteroid was named by its discoverer after Empress Eugénie de 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]

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.[16] 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.[17]

Depiction of 45 Eugenia's satellite orbits.
Visual depiction of the orbits of Petit-Prince and S/2004 (45) 1 around 45 Eugenia

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[18] and is informally dubbed "Petite-Princesse".[19] 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.[18]

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

Notes

  1. ↑ Uncertainty calculated from uncertainties in the orbit of Petit-Prince
  2. ↑ 2.0 2.1 On the extremities of the long axis

See also

References

  1. ↑ "Discovery Circumstances: Numbered Minor Planets". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. 9 February 2010. http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html. 
  2. ↑ Eugenia (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=Eugenia  (Subscription or UK public library membership required.)
  3. ↑ "ASTORB". Orbital elements database. Lowell Observatory. http://ftp.lowell.edu/pub/elgb/astorb.html. 
  4. ↑ 4.0 4.1 4.2 Baer, Jim (2008). "Recent Asteroid Mass Determinations". Personal Website. http://home.earthlink.net/~jimbaer1/astmass.txt. 
  5. ↑ 5.0 5.1 5.2 5.3 "Supplemental IRAS minor planet survey". Planetary Science Institute. http://www.psi.edu/pds/resource/imps.html. 
  6. ↑ 6.0 6.1 6.2 Kaasalainen, M. (2002). "Models of Twenty Asteroids from Photometric Data". Icarus 159 (2): 369–395. doi:10.1006/icar.2002.6907. Bibcode: 2002Icar..159..369K. http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf. 
  7. ↑ 7.0 7.1 7.2 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. ↑ Marchis, F.. "synthesis of several observations". Berkeley. http://astro.berkeley.edu/~fmarchis/Science/Asteroids/Eugenia.html. 
  9. ↑ 9.0 9.1 Marchis, F. (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. ↑ "PDS lightcurve data". Planetary Science Institute. http://www.psi.edu/pds/resource/lc.html. 
  11. ↑ "PDS node taxonomy database". Planetary Science Institute. http://www.psi.edu/pds/resource/taxonomy.html. 
  12. ↑ 12.0 12.1 Schmadel, Lutz D. (2003). Dictionary of minor planet names. Physics and astronomy online library (5th ed.). Springer. p. 19. ISBN 3-540-00238-3. https://archive.org/details/dictionaryminorp00schm. 
  13. ↑ J. C. (1867). "Obituary: Herman Goldschmidt". Memoirs of the Royal Astronomical Society 36: 114–117. https://books.google.com/books?id=Q6wRAAAAYAAJ&pg=PT115. Retrieved 2010-08-13. 
  14. ↑ Goldschmidt, H. (July 1857). "New Planet (45)". Monthly Notices of the Royal Astronomical Society 17: 263–264. doi:10.1093/mnras/17.9.263b. Bibcode: 1857MNRAS..17..263G. 
  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. ↑ Rivkin, A. S. (2002). "Calculated Water Concentrations on C Class Asteroids". Lunar and Planetary Institute. https://www.lpi.usra.edu/meetings/lpsc2002/pdf/1414.pdf. 
  17. ↑ William J. Merlin et al., "On a Permanent Name for Asteroid S/1998(45)1". 26 May 2000.
  18. ↑ 18.0 18.1 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. 
  19. ↑ [1]
  20. ↑ "IMCCÉ Breaking News". http://www.imcce.fr/page.php?nav=en%2Factualites%2Factu.php%3Fid%3D139. 

Template:Antoine de Saint-Exupéry



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