52 Europa
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52 Europa is the sixth-largest asteroid in the asteroid belt, having a diameter of over 300 km, though it is not correspondingly massive. It is shaped like an ellipsoid with approximate dimensions of 380×330×250 km.[1] It was discovered on 4 February 1858, by Hermann Goldschmidt from his balcony in Paris. It is named after Europa, one of Zeus's conquests in Greek mythology, a name it shares with Jupiter's moon Europa.
Orbit
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Europa is a main belt asteroid that orbits the Sun at a distance of 2.746–3.442 astronomical units (AU) with a semi-major axis or average orbital distance of 3.094 AU once every 5.44 years[2] (for reference, Ceres's orbit is at 2.77 AU).[3]
Europa's orbit has an eccentricity of 0.1125 and an inclination of 7.482° with respect to the ecliptic.[2]
Physical characteristics
Europa is approximately the sixth largest asteroid by volume. Most likely it has a density of around 1.5 g/cm3, typical of C-type asteroids.[1] In 2007, James Baer and Steven R. Chesley estimated Europa to have a mass of Template:Val kg.[4] A more recent estimate by Baer suggests it has a mass of 3.27Template:E kg.[5]
Europa is a very dark carbonaceous C-type, and is the second largest of this group. Spectroscopic studies have found evidence of olivines and pyroxenes on the surface,[6] and there is some indication that there may be compositional differences between different regions.[7] It orbits close to the Hygiea asteroid family, but is not a member.
Lightcurve data for Europa have been particularly tricky to interpret, so much so that for a long time its period of rotation was in dispute (ranging from Template:Frac hours to 11 hours), despite numerous observations.[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.[9] This gives an axial tilt of about 14° or 54°, respectively.
In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Maunakea Observatories, but the effort came up empty.[10]
Observations
The reputed cataclysmic variable star CV Aquarii, discovered in 1934 by Emily Hughes at Harvard College Observatory, was actually a misidentification of 52 Europa.[11]
Notes
References
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Bibliography
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- Schmeer, P., and M. L. Hazen, CV Aquarii identified with (52) Europa, Journal of the American Association of Variable Star Observers, Vol. 28, p. 103 (2000).
External links
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