45 EUGENIA

'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.

Contents

Discovery

Physical characteristics

Satellite system

See also

External links

References

Discovery

Eugenia was discovered 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 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.
Lightcurve analysis indicates that Eugenia's pole most likely points towards ecliptic coordinates (β, λ) = (-30°, 124°) with a 10° uncertainty , which gives it an axial tilt of 117°. Eugenia's rotation is then retrograde.

Satellite system

===Petit-Prince===
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 asteroidal moon had been discovered 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) satellite that orbits closer to Eugenia than Petit-Prince has since been discovered and provisionally named S/2004 (45) 1http://adsabs.harvard.edu/abs/2007IAUC.8817....1M IAUC 8817. 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 IMCCÉ Breaking News. The discovery was announced in IAUC 8817, on 7 March 2007 by Franck Marchis and his IMCCE collaborators.

See also

Dactyl and Ida - Another asteroid and asteroid moon system catalogued by astronomers

External links

★ 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)

References

1. Discovery Circumstances: Numbered Minor Planets, Minor Planet Centre
2. [ftp://ftp.lowell.edu/pub/elgb/astorb.html ASTORB] orbital elements database, Lowell Observatory
3. Supplemental IRAS Minor Planet Survey
4. ''Models of Twenty Asteroids from Photometric Data'', M. Kaasalainen et al, , , Icarus, 2002
5. synthesis of several observations, F. Marchis.
6. ''Fine Analysis of 121 Hermione, 45 Eugenia, and 90 Antiope Binary Asteroid Systems With AO Observations'', F. Marchis et al, , , Bulletin of the American Astronomical Society, 2004
7. Uncertainty calculated from uncertainties in the orbit of Petit-Prince.
8. PDS lightcurve data