52 Europa
 Star field showing asteroid Europa | |
| Discovery | |
|---|---|
| Discovered by | H. Goldschmidt |
| Discovery date | February 4, 1858 |
| Designations | |
| Pronunciation | /jʊˈroʊpə/ ew-ROH-pə |
| Named after | Europa |
| Alternative names | 1948 LA |
| Minor planet category | Main belt |
| Orbital characteristics | |
| Epoch November 26, 2005 (JD 2453700.5) | |
| Aphelion | 3.417 AU (511.201 Gm) |
| Perihelion | 2.785 AU (416.621 Gm) |
| Semi-major axis | 3.101 AU (463.911 Gm) |
| Eccentricity | 0.102 |
| Orbital period | 5.46 a (1994.629 d) |
| Average orbital speed | 16.87 km/s |
| Mean anomaly | 70.730° |
| Inclination | 7.466° |
| Longitude of ascending node | 128.992° |
| Argument of perihelion | 343.553° |
| Physical characteristics | |
| Dimensions |
360×315×240 km[1] 379×330×249 km[2] |
| Mass | 3.27×1019 kg[3] |
| Mean density | 1.5 ± 0.4 g/cm³[2] |
| Equatorial surface gravity | ~0.14 m/s² |
| Escape velocity | ~0.2 km/s |
| Rotation period | 0.2347 d |
| Albedo | 0.058 [1] |
| Temperature |
~173 K max: 258K (-15 °C) |
| Spectral type | C-type asteroid |
| Absolute magnitude (H) | 6.31 |
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52 Europa is one of the larger asteroids in the asteroid belt, having an average diameter of around 315 km. The body is not round but is shaped like a triaxial ellipsoid of approximately 380x330x250 km.[2] 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.[2] In 2007, James Baer and Steven R. Chesley estimated Europa to have a mass of (1.9±0.4)×1019 kg.[1] A more recent estimate by Baer suggests it has a mass of 3.27×1019 kg.[3]
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,[5] and there is some indication that there may be compositional differences between different regions It orbits close to the Hygiea asteroid family, but is not a member.
Lightcurve data for Europa has 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.[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.[2]. 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.[4]
Observations
It has been found that the reputed cataclysmic variable star CV Aquarii, discovered in 1934, was actually a misidentification of 52 Europa.
Footnotes
- ↑ 1.0 1.1 Baer, James; Steven R. Chesley (2007). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris" (PDF). Celestial Mechanics and Dynamical Astronomy (Springer Science+Business Media B.V. 2007) 100 (2008): 27–42. Bibcode:2008CeMDA.100...27B. doi:10.1007/s10569-007-9103-8. Retrieved 2008-11-15.
- ↑ 2.0 2.1 2.2 2.3 Merline, W.J.; and many others (2013). The Resolved Asteroid Program - Size, shape, and pole of (52) Europa (PDF). Retrieved 2013-01-24.
- ↑ 3.0 3.1 Baer, James (2008). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2008-11-29.
- ↑ Gradie, J.; Flynn, L. (March 1988), "A Search for Satellites and Dust Belts Around Asteroids: Negative Results", Abstracts of the Lunar and Planetary Science Conference 19: 405–406, Bibcode:1988LPI....19..405G.
References
- Michałowski, T., et al. Photometry and models of selected main belt asteroids I. 52 Europa, 115 Thyra, and 382 Dodona, Astronomy & Astrophysics, Vol. 416, p. 353 (2004).
- PDS lightcurve data
- Dotto, E., et al. ISO results on bright Main Belt asteroids: PHT–S observations, Astronomy & Astrophysics, Vol. 358, p. 1133 (2000).
- Sawyer, S. R., A High-Resolution CCD Spectroscopic Survey of Low-Albedo Main Belt Asteroids, PhD thesis, The University of Texas (1991).
- 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).
- Zappalà, V.; 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
- "Elements and Ephemeris for (52) Europa". Retrieved 2011-05-26.
- shape model deduced from lightcurve
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