45 Eugenia
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
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Discovery[1] and designation
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| Discovered by | H. Goldschmidt | |||||||||
| Discovery date | 27 June 1857 | |||||||||
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Designations
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| Pronunciation | /juːˈdʒiːniə/ ew-jee-nee-ə | |||||||||
| Named after | Empress Eugénie | |||||||||
| Alternate name(s) | 1941 BN | |||||||||
| Minor planet category |
Main belt | |||||||||
| Epoch November 26, 2005 (JD 2453701.5) | ||||||||||
| Aphelion | 440.305 Gm (2.943 AU) | |||||||||
| Perihelion | 373.488 Gm (2.497 AU) | |||||||||
| Semi-major axis | 406.897 Gm (2.720 AU) | |||||||||
| Eccentricity | 0.082 | |||||||||
| Orbital period | 1638.462 d (4.49 a) | |||||||||
| Average orbital speed | 18.03 km/s | |||||||||
| Mean anomaly | 45.254° | |||||||||
| Inclination | 6.610° | |||||||||
| Longitude of ascending node | 147.939° | |||||||||
| Argument of perihelion | 85.137° | |||||||||
| Satellites | Petit-Prince S/2004 (45) 1 |
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| Dimensions | 232 × 193 × 161 km[3] 305 × 220 × 145 km[4][5] |
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| 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] |
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| Mean density | 1.1 ± 0.1 g/cm³[3] 1.1 ± 0.3 g/cm³[7] |
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| Equatorial surface gravity | 0.017 m/s²[9] | |||||||||
| Equatorial escape velocity | 0.071 km/s[9] | |||||||||
| Sidereal rotation period |
0.2375 d (5.699 h)[10] | |||||||||
| Axial tilt | 117 ± 10° | |||||||||
| Pole ecliptic latitude | -30 ± 10°[5] | |||||||||
| Pole ecliptic longitude | 124 ± 10° | |||||||||
| Geometric albedo | 0.040 ± 0.002[4] | |||||||||
| Surface temp. Kelvin Celsius |
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| Spectral type | F[11] | |||||||||
| Absolute magnitude (H) | 7.46[4] | |||||||||
45 Eugenia is a large main-belt asteroid. 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.
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[edit] Discovery
Eugenia was discovered on June 28, 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]
[edit] 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° uncertainty,[5] which gives it an axial tilt of 117°. Eugenia's rotation is then retrograde.
[edit] Satellite system
[edit] Petit-Prince
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Main article: Petit-Prince (moon)
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 discovers 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]
[edit] 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.[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.
[edit] See also
- Dactyl and Ida, another asteroid and asteroid moon system catalogued by astronomers
[edit] References
- ^ "Discovery Circumstances: Numbered Minor Planets". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. February 9, 2010. http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html. Retrieved 2010-08-12.
- ^ "ASTORB". Orbital elements database. Lowell Observatory. ftp://ftp.lowell.edu/pub/elgb/astorb.html.
- ^ a b c Baer, Jim (2008). "Recent Asteroid Mass Determinations". Personal Website. http://home.earthlink.net/~jimbaer1/astmass.txt. Retrieved 2008-12-07.
- ^ a b c d "Supplemental IRAS Minor Planet Survey". http://www.psi.edu/pds/resource/imps.html.
- ^ a b c Kaasalainen, M.; et al. (2002). "Models of Twenty Asteroids from Photometric Data". Icarus 159 (2): 369. Bibcode 2002Icar..159..369K. doi:10.1006/icar.2002.6907. http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf.
- ^ Marchis, F.. "synthesis of several observations". Berkeley. http://astro.berkeley.edu/~fmarchis/Science/Asteroids/Eugenia.html.
- ^ 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.
- ^ Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
- ^ a b On the extremities of the long axis.
- ^ "PDS lightcurve data". Planetary Science Institute. http://www.psi.edu/pds/resource/lc.html.
- ^ "PDS node taxonomy database". Planetary Science Institute. http://www.psi.edu/pds/resource/taxonomy.html.
- ^ 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.
- ^ J. C. (1867). "Memoirs of the Royal Astronomical Society". Memoirs of the Royal Astronomical Society (Priestley and Weale) 36: 155. http://books.google.com/books?id=Q6wRAAAAYAAJ&pg=PT155. Retrieved 2010-08-13.
- ^ Goldschmidt, H. (July 1857). "New Planet (45)". Monthly Notices of the Royal Astronomical Society 17: 263. Bibcode 1857MNRAS..17..263G.
- ^ 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.
- ^ 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. Retrieved 2008-05-22.
- ^ William J. Merlin et al, "On a Permanent Name for Asteroid S/1998(45)1". May 26, 2000.
- ^ http://adsabs.harvard.edu/abs/2007IAUC.8817....1M IAUC 8817
- ^ IMCCÉ Breaking News
[edit] 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)
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