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45 Eugenia

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.

45 Eugenia
Discovery[1]
Discovered byH. Goldschmidt
Discovery date27 June 1857
Designations
1941 BN
Main belt
Orbital characteristics[2]
Epoch November 26, 2005 (JD 2453701.5)
Aphelion440.305 Gm (2.943 AU)
Perihelion373.488 Gm (2.497 AU)
406.897 Gm (2.720 AU)
Eccentricity0.082
1638.462 d (4.49 a)
18.03 km/s
45.254°
Inclination6.610°
147.939°
85.137°
Known satellitesPetit-Prince
S/2004 (45) 1
Physical characteristics
Dimensions305×220×145 km [3][4]
Mean radius
107.3 ± 2.1 km [3]
Mass5.8 ± 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]
0.2375 d (5.699 h) [9]
117 ± 10°
-30 ± 10°[4]
124 ± 10°
0.040 ± 0.002 [10]
Surface temp. min mean max
Kelvin ~171 253
Celsius -22°
F [11]
7.46 [3]

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).

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.

Moons

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.

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.[12] 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.[13] The discovery was announced in IAUC 8817, on 7 March 2007 by Franck Marchis and his IMCCE collaborators.

Other websites

References

  1. ↑ Discovery Circumstances: Numbered Minor Planets, Minor Planet Centre Archived 2008-05-10 at the Wayback Machine
  2. ↑ ASTORB[dead link] orbital elements database, Lowell Observatory
  3. ↑ 3.0 3.1 3.2 "Supplemental IRAS Minor Planet Survey". Archived from the original on 2010-01-17. Retrieved 2007-12-21.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  4. ↑ 4.0 4.1 4.2 M. Kaasalainen; et al. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus. 159 (2): 369. doi:10.1006/icar.2002.6907. Archived from the original (PDF) on 2008-02-16. Retrieved 2007-12-21.
  5. ↑ synthesis of several observations, F. Marchis. Archived 2007-07-24 at the Wayback Machine
  6. ↑ 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. Bibcode:2004DPS....36.4602M.
  7. ↑ Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
  8. ↑ 8.0 8.1 On the extremities of the long axis.
  9. ↑ "PDS lightcurve data". Archived from the original on 2010-01-17. Retrieved 2007-12-21.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  10. ↑ Supplemental IRAS minor planet survey Archived 2009-08-17 at the Wayback Machine
  11. ↑ PDS node taxonomy database Archived 2007-03-10 at the Wayback Machine
  12. ↑ http://adsabs.harvard.edu/abs/2007IAUC.8817....1MIAUC 8817 Archived 2007-06-26 at WebCite
  13. ↑ "IMCCÉ Breaking News". Archived from the original on 2012-03-20. Retrieved 2020-09-14.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
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