|Discovery and designation|
|Discovered by||Jean-Luc Margot and Michael E. Brown|
|Discovery date||August 29, 2001|
|MPC designation||S/2001 (22) 1|
|Minor planet category||Main belt|
<0.015 <0.005 
|Average orbital speed||21.5 m/s|
(undetectable with respect to Kalliope equator)
|Satellite of||22 Kalliope|
|Dimensions||28 ± 2 km|
~6×1016 kg (estimate)~4×1016 kg (estimate)
|Mean density||3.4 g/cm3 (assumed)|
|Equatorial escape velocity||~20 m/s (estimate)|
|Rotation period||unknown, probably synchronous|
|Axial tilt||unknown, zero expected|
|Absolute magnitude (H)||9.7 |
(22) Kalliope I Linus is an asteroid moon that orbits the large M-type asteroid 22 Kalliope. It was discovered on August 29, 2001, by astronomers Jean-Luc Margot and Michael E. Brown with the Keck telescope. Another team also detected the moon with the Canada-France-Hawaii Telescope on September 2, 2001. Both telescopes are on Mauna Kea. It received the provisional designation S/2001 (22) 1, until it was named. The naming proposal appeared in the discovery paper and was approved by the International Astronomical Union in July 2003. Although the naming proposal referred to the mythological Linus, son of the muse Calliope and the inventor of melody and rhythm, the name was also meant to honor Linus Torvalds, inventor of the Linux operating system, and Linus van Pelt, a character in the Peanuts comic strip.
With an estimated 28 ± 2 km diameter, Linus is very large compared to most asteroid moons, and in fact would be a sizable asteroid by itself. The only known larger moons in the main belt are the smaller components of the double asteroids 617 Patroclus and 90 Antiope.
It has been estimated that Linus' orbit precesses at quite a rapid rate, making one cycle in several years. This is attributed primarily to the non-spherical shape of Kalliope. Linus's brightness has varied appreciably between observations, which may indicate that its shape is elongated.
- "IAUC 7703: S/2001 (22) 1; 2001ed". IAU Central Bureau for Astronomical Telegrams. September 3, 2001. Retrieved 2012-07-18.
- J.L. Margot & M.E. Brown (2003). "A Low-Density M-type Asteroid in the Main Belt". Science 300 (5627): 1939–42. Bibcode:2003Sci...300.1939M. doi:10.1126/science.1085844. PMID 12817147.
- 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.
- synthesis of several observations including recent ones with the VLT 8m telescope.
- Based on a rough tidal locking timescale of several tens of My.
- F. Marchis et al. (2003). "A three-dimensional solution for the orbit of the asteroidal satellite of 22 Kalliope". Icarus 165 (1): 112. Bibcode:2003Icar..165..112M. doi:10.1016/S0019-1035(03)00195-7.
- "IAUC 8177: Sats of (22); Sats of Jupiter, Saturn, Uranus". IAU Central Bureau for Astronomical Telegrams. August 8, 2003. Retrieved 2012-07-18.
- Margot, Jean-Luc (2004). "Adaptive Optics Observations of Kalliope-Linus". UCLA. Retrieved 2013-08-30.
- IAUC 7703: S/2001 (22) 1, announcing Linus' discovery (2001 September 3)
- IAUC 8177: Sats of (22); Sats of Jupiter, Saturn, Uranus, announcing Linus' naming (2003 August 8)
- Link to the Linus discovery paper , "A Low-Density M-type Asteroid in the Main Belt"
- Kalliope and Linus very well resolved with the 8m VLT
- orbit diagram for Linus
- Information on Kalliope, Linus' orbit and several images
- A different VLT image of Kalliope and Linus
- another image of Kalliope and Linus