45 Eugenia

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45 Eugenia
Discovery and designation [1]
Discovered byH. Goldschmidt
Discovery date27 June 1857
Names
Other names1941 BN
CategoryMain belt
Orbit [2]
Reference date November 26, 2005 (JD 2453701.5)
Longest distance from the Sun440.305 Gm (2.943 AU)
Shortest distance from the Sun373.488 Gm (2.497 AU)
Longest distance from the center of its orbital path
("semi-major axis")
406.897 Gm (2.720 AU)
How long it takes to complete an orbit1638.462 d (4.49 a)
Average speed18.03 km/s
Mean anomaly45.254°
Angle above the reference plane
("inclination")
6.610°
Natural things that orbit itPetit-Prince
S/2004 (45) 1
Size and other qualities
Measurements305×220×145 km [3][4]
Average radius107.3 ± 2.1 km [3]
Mass5.8 ± 0.2 ×1018 kg [5][6][7]
Average density1.1 ± 0.3 g/cm³ [6]
Surface gravity0.017 m/s²[8]
Escape velocity0.071 km/s[8]
Angle at which it turns
(in relation to its orbit)
117 ± 10°
How much light it reflects0.040 ± 0.002 [9]
Surface temp. Min. Avg. Max.
Kelvin ~171 253
Celsius -22°
Spectral typeF [10]
True brightness
("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.

Discovery[change | change source]

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[change | change source]

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[change | change source]

Petit-Prince[change | change source]

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[change | change source]

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.

Other websites[change | change source]

References[change | change source]