45 Eugenia

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45 Eugenia
Discovery and designation [1]
Discovered by H. Goldschmidt
Discovery date 27 June 1857
Other names 1941 BN
Category Main belt
Orbit [2]
Reference date November 26, 2005 (JD 2453701.5)
Longest distance from the Sun 440.305 Gm (2.943 AU)
Shortest distance from the Sun 373.488 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 orbit 1638.462 d (4.49 a)
Average speed 18.03 km/s
Mean anomaly 45.254°
Angle above the reference plane
Natural things which orbit it Petit-Prince
S/2004 (45) 1
Size and other qualities
Measurements 305×220×145 km [3][4]
Average radius 107.3 ± 2.1 km [3]
Mass 5.8 ± 0.2 ×1018 kg [5][6][7]
Average density 1.1 ± 0.3 g/cm³ [6]
Surface gravity 0.017 m/s²[8]
Escape velocity 0.071 km/s[8]
Angle at which it turns
(in relation to its orbit)
117 ± 10°
How much light it reflects 0.040 ± 0.002 [9]
Surface temp. Min. Avg. Max.
Kelvin ~171 253
Celsius -22°
Spectral type F [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]