Astronomy:45 Eugenia

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Short description: Asteroid with 2 moons
45 Eugenia
45 Eugenia VLT (2021), deconvolved.pdf
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 Gm (2.943 AU)
|{{{apsis}}}|helion}}373.488 Gm (2.497 AU)
406.897 Gm (2.720 AU)
Eccentricity0.082
Orbital period1638.462 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][10]
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[11]
Equatorial escape velocity
0.071 km/s[11]
Sidereal rotation period0.2375 d (5.699 h)[12]
Axial tilt117±10°
Pole ecliptic latitude−30±10°[6]
Pole ecliptic longitude124±10°
Geometric albedo0.065 (calculated)[7]
0.040±0.002[5]
F[13]
Absolute magnitude (H)7.46[5]


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.

Discovery

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

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" (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

  • Dactyl and Ida, another asteroid and asteroid moon system catalogued by astronomers
  • Florence, another dual-moon asteroid confirmed only in September 2017.

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. ↑ Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
  11. ↑ 11.0 11.1 On the extremities of the long axis.
  12. ↑ "PDS lightcurve data". Planetary Science Institute. http://www.psi.edu/pds/resource/lc.html. 
  13. ↑ "PDS node taxonomy database". Planetary Science Institute. http://www.psi.edu/pds/resource/taxonomy.html. 
  14. ↑ 14.0 14.1 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. 
  15. ↑ 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. 
  16. ↑ 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. 
  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". Lunar and Planetary Institute. http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1414.pdf. 
  19. ↑ William J. Merlin et al., "On a Permanent Name for Asteroid S/1998(45)1". 26 May 2000.
  20. ↑ 20.0 20.1 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". http://www.imcce.fr/page.php?nav=en%2Factualites%2Factu.php%3Fid%3D139. 

External links



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