|
52 Europa is the 6th-largest asteroid in the asteroid belt, having an average diameter of around 315 km. It is not round but is shaped like a triaxial ellipsoid of approximately 380x330x250 km.〔〕 It was discovered on February 4, 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. ==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.〔 In 2007, James Baer and Steven R. Chesley estimated Europa to have a mass of (1.9±0.4) kg. A more recent estimate by Baer suggests it has a mass of 3.27 kg. 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,〔 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〕 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 5 and a half hours to 11 hours), despite numerous observations.〔 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.〔 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 Mauna Kea Observatories, but the effort came up empty. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「52 Europa」の詳細全文を読む スポンサード リンク
|