22 Kalliope

From Wikipedia, the free encyclopedia
Jump to: navigation, search
22 Kalliope
22-Kalliope-Linus.jpg
Kalliope and satellite Linus as seen by the W.M. Keck II telescope in 2010
Discovery
Discovered by John Russell Hind
Discovery date November 16, 1852
Designations
Pronunciation /kəˈl.əp/ kə-LY-ə-pee
Named after
Calliopē
none
Minor planet category Main belt
Orbital characteristics[1]
Epoch 2010-Jul-23 (JD 2455400.5)
Aphelion 479.98 Gm
3.2085 AU
Perihelion 391.03 Gm
2.6139 AU
435.09 Gm
2.9112 AU
Eccentricity 0.10213
1814.3 d (4.97 yr)
17.42 km/s
282.54°
Inclination 13.703°
66.17°
355.03°
Known satellites Linus
Physical characteristics
Dimensions 235×144×124 km[2]
166.2±2.8 km[2]
181 ± 4.6 km (IRAS)[1]
Mean radius
83.1 ± 1.4 km[2]
Mass 8.16 ± 0.26×1018 kg
Mean density
3.35 ± 0.33 g/cm³[2]
0.079 m/s²
0.114 km/s
0.1728 d (4.148 h)[1]
Albedo 0.17[2]
Temperature ~161 K
max: 240 K (−32 °C)
Spectral type
M (Tholen)[1]
6.45[1]

22 Kalliope[3] is a large M-type asteroid from the asteroid belt discovered by J. R. Hind on November 16, 1852. It is named after Calliope, the Greek Muse of epic poetry. It is orbited by a small moon named Linus.

Characteristics[edit]

Kalliope is somewhat elongated, approximately 166 km in diameter,[2] and slightly asymmetric, as evidenced by resolved images taken with the VLT at the European Southern Observatory. This new diameter, which was measured by observing mutual eclipses of Kalliope and Linus, is smaller by 8% than that determined by the IRAS satellite in 1980s.[2]

The spectrum of Kalliope is an M-type, indicating that its surface may be partially composed of ironnickel metal. The asteroid's density is about 3.4 g/cm3.[2] Since the asteroid is likely to be a rubble pile, accounting for a possible porosity of 20–40% leads to the material density of 4.2–5.8 g/cm3, which means that Kalliope is probably made of a mixture of metal with silicates.[2] Spectroscopic studies have shown, however, evidence of hydrated minerals[4] and silicates,[5] which indicate rather a stony surface composition. Kalliope also has a low radar albedo,[6] which is inconsistent with a purely metallic surface.

Lightcurve analysis indicates that Kalliope's pole most likely points towards ecliptic coordinates (β, λ) = (−23°, 20°) with a 10° uncertainty,[7][8] which gives Kalliope an axial tilt of 103°. Kalliope's rotation is then slightly retrograde.

Satellite[edit]

Kalliope has one known natural satellite, Linus, or (22) Kalliope I Linus. It is quite large, being about 28 km in diameter, and would be a sizeable asteroid by itself. It orbits about 1100 km from the center of Kalliope, equivalent to about 13.2 Kalliope radii.[2] Linus was discovered on August 29, 2001 by Jean-Luc Margot and Michael E. Brown, while another team led by William Merline also independently detected the moon 3 days later.[6][8]

First stellar occultation[edit]

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[edit]

  1. ^ a b c d e "JPL Small-Body Database Browser: 22 Kalliope". 2010-06-02 last obs. Retrieved 2010-07-22. 
  2. ^ a b c d e f g h i j Descamps, P.; Marchis, F. et al. (2008). "New determination of the size and bulk density of the binary asteroid 22 Kalliope from observations of mutual eclipses". Icarus 196 (2): 578–600. arXiv:0710.1471. Bibcode:2008Icar..196..578D. doi:10.1016/j.icarus.2008.03.014. 
  3. ^ Pronounced /kəˈl.əp/ kə-LY-ə-pee
  4. ^ A.S. Rivkin (2000). "The nature of M-class asteroids from 3-micron observations". Icarus 145 (2): 351–368. Bibcode:2000Icar..145..351R. doi:10.1006/icar.2000.6354. 
  5. ^ D.F. Lupishko (1982). "UBV photometry of the M-type asteroids 16 Psyche and 22 Kalliope". Solar System Research 16: 75. 
  6. ^ a b J.L. Margot & M.E. Brown (2003). "A Low-Density M-type Asteroid in the Main Belt". Science 300 (5627): 1939–1942. Bibcode:2003Sci...300.1939M. doi:10.1126/science.1085844. PMID 12817147. 
  7. ^ M. Kaasalainen (2002). "Models of Twenty Asteroids from Photometric Data". Icarus 159 (2): 369–395. Bibcode:2002Icar..159..369K. doi:10.1006/icar.2002.6907. 
  8. ^ a b F. Marchis (2003). "A three-dimensional solution for the orbit of the asteroidal satellite of 22 Kalliope". Icarus 165 (1): 112–120. Bibcode:2003Icar..165..112M. doi:10.1016/S0019-1035(03)00195-7. 
  9. ^ M. Soma et al. (2006). "'Occulation by Kalliope and Linus". CBET 732: 1. Bibcode:2006CBET..732....1S. 
  10. ^ J. Berthier et al. (2004). "'Prediction of stellar occultations by satellite of asteroids". Dps-Aas. 32.23: 1142. Bibcode:2004DPS....36.3223B. 

External links[edit]