45 Eugenia

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0 | minorplanet=yes | width=25em
name=45 Eugenia
discovery_ref = [ [http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html Discovery Circumstances: Numbered Minor Planets] , Minor Planet Centre]
discoverer=H. Goldschmidt
discovered=27 June, 1857
alt_names=1941 BN
mp_category=Main belt
orbit_ref = [ [ftp://ftp.lowell.edu/pub/elgb/astorb.html ASTORB] orbital elements database, Lowell Observatory]
epoch=November 26, 2005 (JD 2453701.5)
semimajor=406.897 Gm (2.720 AU)
perihelion=373.488 Gm (2.497 AU)
aphelion=440.305 Gm (2.943 AU)
eccentricity=0.082
period=1638.462 d (4.49 a)
inclination=6.610°
asc_node=147.939°
arg_peri=85.137°
mean_anomaly=45.254°
avg_speed=18.03 km/s
satellites = Petit-Prince
S/2004 (45) 1
dimensions=305×220×145 km [http://www.psi.edu/pds/resource/imps.html Supplemental IRAS Minor Planet Survey] ] cite journal | author= M. Kaasalainen et al| title= "Models of Twenty Asteroids from Photometric Data"| journal= Icarus| year= 2002| volume= 159| pages= 369| url= http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf | doi= 10.1006/icar.2002.6907]
mean_radius = 107.3 ± 2.1 km
mass=5.8 ± 0.2 e|18 kg [http://astro.berkeley.edu/~fmarchis/Science/Asteroids/Eugenia.html synthesis of several observations] , F. Marchis. ] cite journal | author= F. Marchis et al| title= "Fine Analysis of 121 Hermione, 45 Eugenia, and 90 Antiope Binary Asteroid Systems With AO Observations"| journal= Bulletin of the American Astronomical Society| year= 2004| volume= 36| pages= 1180|url=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.]
density=1.1 ± 0.3 g/cm³
surface_grav=0.017 m/s²On the extremities of the long axis.]
escape_velocity=0.071 km/s
sidereal_day=0.2375 d (5.699 h) [http://www.psi.edu/pds/resource/lc.html PDS lightcurve data] ]
axial_tilt = 117 ± 10°
pole_ecliptic_lat = -30 ± 10°
pole_ecliptic_lon = 124 ± 10°
temperatures=yes
temp_name1 = Kelvin
mean_temp_1 = ~171
max_temp_1 = 253
temp_name2 = Celsius
max_temp_2 = -22°
albedo= 0.040 ± 0.002 " [http://www.psi.edu/pds/resource/imps.html Supplemental IRAS minor planet survey] "]
spectral_type = F " [http://www.psi.edu/pds/resource/taxonomy.html PDS node taxonomy database] "]
abs_magnitude=7.46

45 Eugenia (IPAEng|juˈdʒiːniə) 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.

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. Eugenia appears to be almost anhydrous.cite web
date=2002
title=Calculated Water Concentrations on C Class Asteroids
publisher=Lunar and Planetary Institute
author=A. S. Rivkin
url=http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1414.pdf
accessdate=2008-05-22]

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.

atellite 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 [http://www.imcce.fr/page.php?nav=en/actualites/actu.php?id=139 IMCCÉ Breaking News] ] . The discovery was announced in IAUC 8817, on 7 March 2007 by Franck Marchis and his IMCCE collaborators.

ee also

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

External links

* [http://www.johnstonsarchive.net/astro/astmoons/am-00045.html Johnston Archive data]
* [http://antwrp.gsfc.nasa.gov/apod/ap991014.html Astronomical Picture of Day] 14 October 1999
* [http://www.boulder.swri.edu/~merline/press_release/ SwRI Press Release]
* [http://astron.berkeley.edu/~fmarchis/Science/Asteroids/#Eugenia Orbit of Petit-Prince, companion of Eugenia]
* [http://cfa-www.harvard.edu/iauc/08100/08177.html IAUC 8177]
* [http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf Shape model derived from lightcurve (on page 17)]

References