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22 Kalliope

22 Kalliope
Discovery
Discovered by John Russell Hind
Discovery date November 16, 1852
Designations
Alternative names none
Minor planet
category		 Main belt
Epoch November 12, 2005 (JD 2453686.5)
Aphelion 479.931 Gm (3.208 AU)
Perihelion 390.433 Gm (2.610 AU)
Semi-major axis 435.182 Gm (2.909 AU)
Eccentricity 0.103
Orbital period 1812.245 d (4.96 a)
Average orbital speed 17.42 km/s
Mean anomaly 303.545°
Inclination 13.710°
Longitude of ascending node 66.240°
Argument of perihelion 356.172°
Physical characteristics
Dimensions 215×180×150 km [1][2]
Mass 6.3 ± 0.5 ×1018 kg [3][4]
Mean density 2.03 ± 0.16 g/cm³ [3]
Equatorial surface gravity 0.038 m/s²
Escape velocity 0.09 km/s
Rotation period 0.1728 d (4.148 h) [5]
Albedo 0.142 [1]
Temperature ~161 K
max: 240 K (-32 °C)
Spectral type M [5]
Absolute magnitude 6.45

22 Kalliope (pronounced /kəˈlaɪəpi/, Greek: Καλλιόπη) is a large main belt asteroid of the M-type, discovered by J. R. Hind on November 16, 1852. It is named after Calliope, the Greek Muse of epic poetry.

Contents

Characteristics

Kalliope is somewhat elongated, approximately 180 km in diameter, and slightly asymmetric, as evidenced by resolved images taken with the VLT at the European Southern Observatory [6].

While its spectrum is an M-type, Kalliope does not appear to be metallic, similarly to other M-types such as 21 Lutetia, for example. Firstly, its density, which is known with confidence from its satellite's orbit, is far too low to agree with any plausible metallic substance, even a rubble pile. It would have to be 70% porous, which is inconsistent with packing considerations. Furthermore, spectroscopic studies have shown evidence of hydrated minerals [7] and silicates [8], which indicate rather a stony surface composition. Kalliope also has a low radar albedo [4], which is again inconsistent with a metallic surface.

Lightcurve analysis indicates that Kalliope's pole most likely points towards ecliptic coordinates (β, λ) = (-23°, 20°) with a 10° uncertainty [2][3], which gives Kalliope an axial tilt of 103°. Kalliope's rotation is then slightly retrograde.

Satellite

Kalliope has one known natural satellite, Linus, or (22) Kalliope I Linus. It is quite large being 30-40 km in diameter, and would be a sizeable asteroid by itself. It orbits about 1065 km from Kalliope, equivalent to about 12 Kalliope radii. Linus was discovered on August 29, 2001 by Jean-Luc Margot and Michael E. Brown, while another team lead by William Merline also independently detected the moon 3 days later. [6]

First Stellar Occultation

On November 7 2006, the first stellar occultation by the satellite of an asteroid (Linus) was successfully observed by a group of Japanese observers [9]according to a prediction that was made just one day before by Berthier et al. [10] based on more than 5 years of regular observations of Kalliope binary system using adaptive optics systems on ground-based telescopes. The observed chords of Linus give a unique opportunity to estimate the size of the moonlet which was estimated to 20-28 km.

References

  1. ^ a b Supplemental IRAS Minor Planet Survey
  2. ^ a b M. Kaasalainen et al (2002). "Models of Twenty Asteroids from Photometric Data". Icarus 159: 369. doi:10.1006/icar.2002.6907. 
  3. ^ a b c F. Marchis et al (2003). "A three-dimensional solution for the orbit of the asteroidal satellite of 22 Kalliope". Icarus 165: 112. doi:10.1016/S0019-1035(03)00195-7. 
  4. ^ a b J.L. Margot & M.E. Brown (2003). "A Low-Density M-type Asteroid in the Main Belt". Science 300: 1939. doi:10.1126/science.1085844. 
  5. ^ a b PDS lightcurve data
  6. ^ a b synthesis of several observations including recent ones with the VLT 8 m telescope.
  7. ^ A.S. Rivkin et al (2000). "The nature of M-class asteroids from 3-micron observations". Icarus 145: 351. doi:10.1006/icar.2000.6354. 
  8. ^ D.F. Lupishko et al (1982). "UBV photometry of the M-type asteroids 16 Psyche and 22 Kalliope". Solar System Research 16: 75. 
  9. ^ M. Soma et al (2006). "'Occulation by Kalliope and Linus"". CBET 732. 
  10. ^ J. Berthier et al. (2004). "'Prediction of stellar occultations by satellite of asteroids"". DPS-AAS 32.23. 

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See also: Near-Earth object · Dwarf planet · Planet · Solar System · Pronunciation of asteroid names · Meanings of asteroid names.
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