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532 HerculinaFrom Wikipedia, the free encyclopedia  (Redirected from Herculina)
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532 Herculina
Discovery
Discovered by	Max Wolf
Discovery date	April 20, 1904
Designations
Alternate name	1904 NY
Minor planet category	Main belt
Orbital characteristics[1]
Epoch 22 November 2003 (JD 2452600.5)
Aphelion	3.26 AU
Perihelion	2.29 AU
Semi-major axis	2.7719820 AU
Eccentricity	0.1777919
Orbital period	4.62 a
Average orbital speed	unknown
Mean anomaly	142.15781°
Inclination	16.30843°
Longitude of ascending node	107.65510°
Argument of perihelion	76.86717°
Physical characteristics
Dimensions	222 km IRAS[1]
Mass	~2.29×1019Kg [2]
Mean density	~4 g/cm³[2]
Equatorial surface gravity	unknown
Escape velocity	unknown
Rotation period	9.404951 h[1]
Albedo	0.16[1]
Temperature	unknown
Spectral type	S[1]
Apparent magnitude	8.82[3] to 11.99
Absolute magnitude (H)	5.81[1]
Angular diameter	0.228" to 0.073"

532 Herculina (pronounced /hɛrkjuˈlaɪnə/ HERR-kew-LYE-nə) is a very large asteroid, with a diameter of around 225 km.

Contents[hide] 1 Discovery 2 Physical characteristics 3 Satellites 4 References 5 External links

[edit] DiscoveryIt was discovered on April 20, 1904, by Max Wolf in Heidelberg, and initially catalogued as 1904 NY.[4] The origin of its name is not known; it may be named after the mythical Hercules, or after an unknown woman of that name. The bulk of the asteroids discovered by Wolf around this date were named for characters in operas, but if this name was also drawn from such a source, no explanation has been recorded.
[edit] Physical characteristicsHerculina is one of the twenty or so largest members of the main asteroid belt.[5]
It has often been noted for its complex lightcurves, which made determination of its shape and rotation somewhat difficult. A set of 1982 speckle interferometry observations led to a simple preliminary model of Herculina as a three-axis object, perhaps 260 by 220 by 215 km. 1985 analysis of this data concluded there was a nonspherical shape with one bright spot, whilst a 1987 photometric astrometry study concluded the object was spherical with two dark spots (and rotated around a completely different pole), which was in turn negated by a 1988 thermal study which showed the object could not be spherical. By the late 1980s, the generally accepted model was a three-axis object with major albedo or topographical features.[6]
Recent (2002) modelling of photometric data indicates that Herculina is not spherical, but a blocky shape not unlike a battered cuboid - or, as the analysis described it, it "resembles a toaster". This analysis indicates the presence of multiple largish craters, similar to 253 Mathilde, but no major variation in albedo. The approximate ratios of the axes were suggested as 1:1.1:1.3, broadly consistent with earlier models if slightly more elongated.[7]
[edit] SatellitesFollowing anomalous observations during an occultation of the star SAO 1220774 in 1978, Herculina became the first asteroid to be "confirmed" to have an asteroid moon, with the parent asteroid estimated at a 216 km diameter and a satellite of about 45 km orbiting at a distance of around 1,000 km.[8] However, careful examination in 1993, using the Hubble Space Telescope, failed to locate a secondary.[9]
[edit] References

• ^ a b c d e f "JPL Small-Body Database Browser: 532 Herculina (1904 NY)". 2008-11-17 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=532. Retrieved 2009-01-23.
  
• ^ a b Masses and densities of minor planets - Yu. Chernetenko, O. Kochetova, and V. Shor
• ^ "Bright Minor Planets 2005". Minor Planet Center. http://www.cfa.harvard.edu/iau/Ephemerides/Bright/2005. Retrieved 2008-05-21.
  
• ^ Provisional elements of the minor planet 1904 NY. J. C. Hammond, Astronomical Journal, vol. 24, iss. 564, p. 105-105 (1904) ADS archive copy
• ^ 20 Largest Asteroids
• ^ Speckle interferometry of asteroids (NASA CR-180438). J. Drummond, Steward Observatory, University of Arizona, May 31, 1988
• ^ Models of Twenty Asteroids from Photometric Data. M. Kaasalainen, J. Torppa, and J. Piironen, Icarus 159, 369–395 (2002).
• ^ Satellite of Minor Planet 532 Herculina Discovered During Occultation. David W. Dunham, The Minor Planet Bulletin, Volume 6, p.13-14 (December 1978) ADS archive copy
• ^ Imaging observations of asteroids with Hubble Space Telescope. Storrs et al., Icarus 137, 260–268 (1999)

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Asteroid beltFrom Wikipedia, the free encycloped iaJump to: navigation, search


The main asteroid belt (shown in white) is located between the orbits of Mars and Jupiter.
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt region is also termed the main belt to distinguish it from other concentrations of minor planets within the Solar System, such as the Kuiper belt and scattered disc.
More than half the mass of the main belt is contained in the four largest objects: Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea. All of these have mean diameters of more than 400 km, while Ceres, the main belt's only dwarf planet, is about 950 km in diameter.[1][2][3][4] The remaining bodies range down to the size of a dust particle. The asteroid material is so thinly distributed that multiple unmanned spacecraft have traversed it without incident. Nonetheless, collisions between large asteroids do occur, and these can form an asteroid family whose members have similar orbital characteristics and compositions. Collisions also produce a fine dust that forms a major component of the zodiacal light. Individual asteroids within the main belt are categorized by their spectra, with most falling into three basic groups: carbonaceous (C-type), silicate (S-type), and metal-rich (M-type).
The asteroid belt formed from the primordial solar nebula as a group of planetesimals, the smaller precursors of the planets. Between Mars and Jupiter, however, gravitational perturbations from the giant planet imbued the planetesimals with too much orbital energy for them to accrete into a planet. Collisions became too violent, and instead of sticking together, the planetesimals shattered. As a result, most of the main belt's mass has been lost since the formation of the Solar System. Some fragments can eventually find their way into the inner Solar System, leading to meteorite impacts with the inner planets. Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter. At these orbital distances, a Kirkwood gap occurs as they are swept into other orbits.