22 Kalliope

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22 Kalliope
Kalliope and satellite Linus as seen by the W.M. Keck II telescope in 2010
Discovered by John Russell Hind
Discovery date16 November 1852
(22) Kalliope
Pronunciation /kəˈləp/ [1]
Named after
Καλλιόπη Kalliopē
Main belt
Adjectives Kalliopean /kəl.əˈpən/
Orbital characteristics [2]
Epoch 23 July 2010 (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)
Inclination 13.703°
Known satellites Linus
Physical characteristics
  • 235 km × 144 km × 124 km [3]
  • 166.2±2.8 km [3]
  • 181±4.6 km (IRAS) [2]
Mean radius
  • 83.1±1.4 km [3]
  • 90.5±2.3 km (IRAS)
Mass (8.16±0.26)×1018  kg
Mean density
  • 3.35±0.33 g/cm3 [3]
  • 2.37±0.4 g/cm3 [4]
0.1728 d (4.148 h) [2]
0.17 [3]
6.45 [2]

    Kalliope [6] (minor planet designation: 22 Kalliope) is a large M-type asteroid from the asteroid belt discovered by J. R. Hind on 16 November 1852. It is named after Calliope, the Greek Muse of epic poetry. It is orbited by a small moon named Linus.



    VLT image of Kalliope Kalliope VLT.png
    VLT image of Kalliope

    Kalliope is somewhat elongated, approximately 166 km in diameter, [3] 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 8% smaller than that calculated from IRAS observations. [3]

    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. [3] 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. [3] Spectroscopic studies have shown, however, 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 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, [9] [10] which gives Kalliope an axial tilt of 103°. Kalliope's rotation is then slightly retrograde.


    Kalliope has one known natural satellite, called Linus or (22) Kalliope I Linus. It is quite large  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. [3] Linus was discovered on 29 August 2001 by Jean-Luc Margot and Michael E. Brown, while another team led by William Merline also independently detected the moon 3 days later. [4] [10]

    First stellar occultation

    On 7 November 2006, the first stellar occultation by the satellite of an asteroid (Linus) was successfully observed by a group of Japanese observers [11] according to a prediction that was made just one day before by Berthier et al. [12] 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.

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    1. "calliope" . Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
    2. 1 2 3 4 5 6 "JPL Small-Body Database Browser: 22 Kalliope" (2010-06-02 last obs). Retrieved 22 July 2010.
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    6. Pronounced /kəˈl.əp/ kə-LY-ə-pee
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