45 Eugenia
| Discovery[1] and Designation | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Discoverer | H. Goldschmidt | |||||||||
| Discovery date | 27 June 1857 | |||||||||
| Alternative names [1] | 1941 BN | |||||||||
| Minor planet category | Main belt | |||||||||
| Orbital characteristics[2] Epoch November 26, 2005 (JD 2453701.5) |
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| 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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| Physical characteristics | ||||||||||
| Dimensions | 305×220×145 km [3][4] | |||||||||
| Mean radius | 107.3 ± 2.1 km [3] | |||||||||
| Mass | 5.8 ± 0.2 ×1018 kg [5][6][7] | |||||||||
| Mean density | 1.1 ± 0.3 g/cm³ [6] | |||||||||
| Equatorial surface gravity | 0.017 m/s²[8] | |||||||||
| Equatorial Escape velocity | 0.071 km/s[8] | |||||||||
| Sidereal rotation period | 0.2375 d (5.699 h) [9] | |||||||||
| Axial tilt | 117 ± 10° | |||||||||
| Pole ecliptic latitude | -30 ± 10°[4] | |||||||||
| Pole ecliptic longitude | 124 ± 10° | |||||||||
| Geometric albedo | 0.040 ± 0.002 [3] | |||||||||
| Surface temperature: Kelvin Celsius |
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| Spectral type | F [10] | |||||||||
| Absolute magnitude | 7.46 [3] | |||||||||
45 Eugenia is a big Main belt asteroid. It is famous because it is 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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[change] Discovery
Eugenia was found in 1857 by Hermann Goldschmidt. It was named after Empress Eugenia di Montijo, the wife of Napoleon III, and was the first asteroid to be named after a real person, rather than a figure from classical legend (although there had been controversy about whether 12 Victoria was really named for the mythological figure or for Queen Victoria).
[change] Physical characteristics
Eugenia is a big 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) made up of carbonate. Like Mathilde, its density appears to be unusually low, indicating that it may be a loosely-packed rubble pile (an asteroid that has been broken apart by a collision and pulled back together by gravity).
Lightcurve analysis indicates that Eugenia's pole most likely points towards ecliptic coordinates (β, λ) = (-30°, 124°) with a 10° uncertainty [4], which gives it an axial tilt of 117°. Eugenia's rotation is then retrograde.
[change] Moons
[change] Petit-Prince
In November 1998, astronomers at the Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, found a small moon orbiting Eugenia. This was the first time a moon orbiting an asteroid had been found by a ground-based telescope. Eugenia's moon has been named (45) Eugenia I Petit-Prince, after Empress Eugenia's son, the Prince Imperial. The moon is much smaller than Eugenia, about 13 km in diameter, and takes five days to complete an orbit around it.
[change] S/2004 (45) 1
A second, smaller (estimated diameter of 6 km) moon that orbits closer to Eugenia than Petit-Prince has since been found and provisionally named S/2004 (45) 1[11]. It was found 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 [12]. The discovery was announced in IAUC 8817, on 7 March 2007 by Franck Marchis and his IMCCE collaborators.
[change] Other websites
- Johnston Archive data
- Astronomical Picture of Day 14 October 1999
- SwRI Press Release
- Orbit of Petit-Prince, companion of Eugenia
- IAUC 8177
- Shape model derived from lightcurve (on page 17)
[change] References
- ↑ Discovery Circumstances: Numbered Minor Planets, Minor Planet Centre
- ↑ ASTORB orbital elements database, Lowell Observatory
- ↑ 3.0 3.1 3.2 3.3 Supplemental IRAS Minor Planet Survey
- ↑ 4.0 4.1 4.2 M. Kaasalainen et al (2002). "Models of Twenty Asteroids from Photometric Data". Icarus 159: 369. http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf.
- ↑ synthesis of several observations, F. Marchis.
- ↑ 6.0 6.1 F. Marchis 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. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004DPS....36.4602M&db_key=AST&data_type=HTML&format=&high=444b66a47d20219.
- ↑ Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
- ↑ 8.0 8.1 On the extremities of the long axis.
- ↑ PDS lightcurve data
- ↑ PDS node taxonomy database
- ↑ http://adsabs.harvard.edu/abs/2007IAUC.8817....1M IAUC 8817
- ↑ IMCCÉ Breaking News
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