22 Kalliope and Linus

  • Orbit model based on 46 positions published in Marchis et al., 2003 (obtained with Lick, Palomar), Margot et al., 2003 (Palomar), plus additional data collected with the Gemini, VLT and Keck telescopes equipped with Adaptive Optics System from April 2002 to December 2006
  • Comparison of the primary shape based upon our pole solution and the shape model published by Kaasalainen et al., 2002
  • Predictions of stellar occultations (see also Berthier et al., AAS-DPS, #32.23, 2004). A stellar occultation visible in Japan on Nov. 7 2006 was successfully observed by Soma et al (CBET, 732, 2006) based on our predicted position.
  • The timing of mutual events between the satellite Linus (D=28 +/-2 km ) and the primary Kalliope (D=166+/-3 km) was predicted by Descamps et al (PSS, 2007) in Nov 2006 and observed successfully in Feb-Mar 2007 (Descamps et al., in press, 2008, http://arXiv.org/abs/0710.1471).

    We derived a new size estimate for Kalliope's primary leading to a significantly higher bulk density (~3.3 g/cc) for this M-type asteroid.


Orbital Elements

 

Orbital Properties Linus & 22 Kalliope
Semi-major axis (a) 1095 +/- 11 km
Inclination (i) ~0 deg w.r.t Primary equator
Eccentricity (e) <0.002
Period (P) 3.596 +/- 0.001 days
Mass Mk 8.1+/-0.2 E18 kg
Density (rho) 3.35 +/- 0.33 g/cm3
Nominal Porosity unk.
  • Prograde orbit
  • No detectable inclination
  • No detectable eccentricity

Observations

Fig 1a:
 Lick-3m and Palomar-5m observations recorded in 2001
VLT/NACO-8m observation.

Linus, companion of 22 Kalliope, is easily detected with AO observations since the Dm of the system is ~3.1 and it orbits at 0.7" away from the primary. With a 8m-class telescope, the primary is resolved (see Fig. 1a).

Our campaign d'observations confirms the low density of this M-type asteroid, indicating either a high porosity (~70%) or a significant portion of hydrated material composition for 22 Kalliope.

 

22 Kalliope Primary - Pole solution and Shape


Fig. 1b: Comparison of 22 Kalliope observed with ESO-NACO (DDT time) and Theoretical Shape model based on Kaasalainen et al., 2002 and a Minnaert law profile.

Prediction of Stellar Occultation by Linus

See Berthier et al., ESOP, 2004 for detail

Fig. 1c: Path of the stellar occultation of 22 Kalliope (red) and Linus (blue) on July 8, 2004

Thanks to G. Blow, Dave B., and several amateur Australian astronomers for attempting to observe the secondary occultation. Observations were unsuccessful because of bad weather conditions.