(22) Kalliope I Linus

Kalliope and satellite Linus as seen by the W.M. Keck II telescope in 2010
Discovered byJean-Luc Margot and Michael E. Brown
Discovery dateAugust 29, 2001
Kalliope I
Named after
S/2001 (22) 1
Main belt
AdjectivesLinian /ˈlɪniən/[2]
Orbital characteristics
1063 ± 23 km[3] (1040-1086) 1099 ± 11 km[4] (1088-1110)
Eccentricity<0.015 [3] <0.005 [5]
3.596 ± 0.040 d[3] (3.556-3.636) 3.590 ± 0.001 d[5] (3.589-3.591)
21.5 m/s
Inclination~0° [3][5]
(undetectable with respect to Kalliope equator)
Satellite of22 Kalliope
Physical characteristics
Dimensions28 ± 2 km[4]
Mass~6×1016 kg (estimate)[3] ~4×1016 kg (estimate)
Mean density
3.4 g/cm3 (assumed)
Equatorial escape velocity
~20 m/s (estimate)
unknown, probably synchronous[3][6]
unknown, zero expected
Surface temp. min mean max
Kelvin ~161 240
Celsius ~ -113 −32°
9.7 [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, in Hawaii. 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,[1] until it was named. The naming proposal appeared in the discovery paper[3] and was approved by the International Astronomical Union in July 2003.[8] 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 kernel, and Linus van Pelt, a character in the Peanuts comic strip.[9]

With an estimated 28 ± 2 km (17 ± 1 mi) diameter,[4] Linus is very large compared to most asteroid moons, and 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.[3][7] Linus's brightness has varied appreciably between observations, which may indicate that its shape is elongated.[7]

Linus may have formed out of impact ejecta from a collision with Kalliope, or a fragment captured after disruption of a parent asteroid (a proto-Kalliope).


  1. ^ a b "IAUC 7703: S/2001 (22) 1; 2001ed". IAU Central Bureau for Astronomical Telegrams. September 3, 2001. Retrieved 2012-07-18.
  2. ^ "linia" = 'of Linus' in Banier (1793) The mythology and fables of the ancients, explain'd from history, v. 1; also in Charles Frederick Partington (1838) The British Cyclopædia of Biography
  3. ^ a b c d e f g h 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.
  4. ^ a b c 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.
  5. ^ a b c synthesis of several observations Archived 2006-08-29 at the Wayback Machine including recent ones with the VLT 8m telescope.
  6. ^ Based on a rough tidal locking timescale of several tens of My.
  7. ^ a b c 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.
  8. ^ "IAUC 8177: Sats of (22); Sats of Jupiter, Saturn, Uranus". IAU Central Bureau for Astronomical Telegrams. August 8, 2003. Retrieved 2012-07-18.
  9. ^ Margot, Jean-Luc (2004). "Adaptive Optics Observations of Kalliope-Linus". UCLA. Retrieved 2013-08-30.

External links[]