52 Europa

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name=52 Europa
discoverer=H. Goldschmidt
discovered=February 04, 1858
alt_names=1948 LA
mp_category=Main belt
epoch=November 26, 2005 (JD 2453700.5)
semimajor=463.911 Gm (3.101 AU)
perihelion=416.621 Gm (2.785 AU)
aphelion=511.201 Gm (3.417 AU)
eccentricity=0.102
period=1994.629 d (5.46 a)
inclination=7.466°
asc_node=128.992°
arg_peri=343.553°
mean_anomaly=70.730°
avg_speed=16.87 km/s
dimensions=360×315×240 km ^{[http://www.psi.edu/pds/archive/simps.html] [http://www.rni.helsinki.fi/~mjk/Micha.pdf]}
mass=5.2±1.8×10¹⁹ kg ^{[http://www.edpsciences.org/articles/aa/pdf/2001/29/aa10228.pdf?access=ok]}
density=3.6±1.2 g/cm³
surface_grav=~0.11 m/s²
escape_velocity=~0.20 km/s
rotation=0.2347 d ^{[http://www.psi.edu/pds/archive/lc.html]}
spectral_type=C-type asteroid
abs_magnitude=6.31
albedo=0.058 ^{[#IRAS| [1]}
single_temperature=~173 K
"max:" 258K (-15 °C) ^{[http://aa.springer.de/papers/0358003/2301133.pdf]}

52 Europa (pronEng|jʊˈroʊpə) is an asteroid. It has a diameter of 301 km, and was discovered on February 4, 1858 by H. Goldschmidt. It is named after Europa, one of Zeus's conquests in Greek mythology. Europa is the seventh largest asteroid by volume and the sixth largest by mass (after Ceres, Vesta, Pallas, Hygiea, and Interamnia) and contains somewhat less than 2% of the mass of the entire main belt.

It is a very dark carbonaceous C-type, and the fourth-largest of these. It orbits close to the Hygiea asteroid family, but is not a member. Spectroscopic studies have found evidence of olivines and pyroxenes on the surface ^{[#Dotto00| [5]} , and there is some indication that there may be compositional differences between different regions ^{[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1991PhDT.......105S&db_key=AST&data_type=HTML&format=&high=444b66a47d24766]}

Lightcurve data for Europa has been particularly tricky to interpret, so much so for a long time its period of rotation was in dispute (5 and a half, or 11 hours?) despite numerous observations ^{[#Zappala83| [8]} . It has now been determined that Europa is a prograde rotator, but the exact direction in which its pole points remains ambiguous. The most detailed analysis indicates that it points either towards about ecliptic coordinates (β, λ) = (70°, 55°) or (40°, 255°) with a 10° uncertainty ^{[#Michalowski04| [2]} . This gives an axial tilt of about 14° or 54°, respectively.

It has been found that reputed cataclysmic variable star CV Aquarii found in 1934, was actually a false misidentification of 52 Europa ^{[http://www.aavso.org/publications/ejaavso/v28n2/103.pdf]} .

52 Europa should not be confused with Jupiter's moon Europa.

References

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[http://www.journals.uchicago.edu/doi/full/10.1086/338320Supplemental IRAS Minor Planet Survey]

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T. Michałowski et al [http://www.rni.helsinki.fi/~mjk/Micha.pdf "Photometry and models of selected main belt asteroids I. 52 Europa, 115 Thyra, and 382 Dodona"] , Astronomy & Astrophysics, Vol. 416, p. 353 (2004).
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G. Michalak [http://www.edpsciences.org/articles/aa/pdf/2001/29/aa10228.pdf?access=ok "Determination of asteroid masses II. (6) Hebe, (10) Hygiea, (15) Eunomia, (52) Europa, (88) Thisbe, (444) Gyptis, (511) Davida and (704) Interamnia"] , Astronomy & Astrophysics, Vol. 374, p. 703 (2001)

# [http://www.psi.edu/pds/archive/lc.html PDS lightcurve data]
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E. Dotto et al " [http://aa.springer.de/papers/0358003/2301133.pdf ISO results on bright Main Belt asteroids: PHT–S observations] ", Astronomy & Astrophysics, Vol. 358, p. 1133 (2000).

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S.R. Sawyer " [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1991PhDT.......105S&db_key=AST&data_type=HTML&format=&high=444b66a47d24766 A High-Resolution CCD Spectroscopic Survey of Low-Albedo Main Belt Asteroids] ", PhD thesis, The University of Texas (1991).
#P. Schmeer and M.L. Hazen " [http://www.aavso.org/publications/ejaavso/v28n2/103.pdf CV Aquarii identified with (52) Europa] ", Journal of the American Association of Variable Star Observers, Vol. 28, p. 103 (2000).
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V. Zappalà, M. di Martino and S. Cacciatori "On the ambiguity of rotational periods of asteroids - The peculiar case of 52 Europa", Icarus, Vol. 56, p. 319 (1983).

External links

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* [http://www.rni.helsinki.fi/~mjk/Micha.pdf shape model deduced from lightcurve]