 Kalliope and satelliteLinus as seen by theW.M. Keck II telescope in 2010 | |
| Discovery | |
|---|---|
| Discovered by | John Russell Hind |
| Discovery date | 16 November 1852 |
| Designations | |
| (22) Kalliope | |
| Pronunciation | /kəˈlaɪ.əpi/kə-LY-ə-pee[1] |
Named after | ΚαλλιόπηKalliopē |
| Main belt | |
| Adjectives | Kalliopean/kəˌlaɪ.əˈpiːən/kə-LY-ə-PEE-ən |
| 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) | |
| 282.54° | |
| Inclination | 13.703° |
| 66.17° | |
| 355.03° | |
| Knownsatellites | Linus |
| Physical characteristics | |
| Dimensions | 235 km × 144 km × 124 km[3] 190 km × 125 km[4] |
| Flattening | 0.41[a] |
| Mass | (7.7±0.4)×1018 kg[5] (8.16±0.26)×1018 kg[3] 7.36×1018 kg[6] (6.30±0.50)×1018 kg[7] |
Meandensity | |
| 0.17285 days (4.1483 h)[2] | |
| 0.198[5] 0.17[3] 0.166 ± 0.005[2] | |
| 6.81[2] | |
22 Kalliope (/kəˈlaɪ.əpi/;kə-LY-ə-pee) is a largeM-type asteroid from theasteroid belt discovered byJ. R. Hind on 16 November 1852. It is named afterCalliope, theGreekMuse ofepic poetry. It is orbited by a small moon namedLinus.
Kalliope is somewhat elongated, approximately 166 km indiameter,[3] and slightly asymmetric, as evidenced by resolved images taken with theVLT at theEuropean Southern Observatory. This new diameter, which was measured by observing mutual eclipses of Kalliope and Linus, is 8% smaller th
an that calculated fromIRAS observations.[3]
The spectrum of Kalliope is anM-type, indicating that its surface may be partially composed ofiron–nickel metal. The asteroid's density is about 3.4 g/cm3.[3] Since the asteroid is likely to be arubble 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 withsilicates.[3] Spectroscopic studies have shown, however, evidence ofhydrated minerals[9] and silicates,[10] 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 towardsecliptic coordinates (β, λ) = (−23°, 20°) with a 10° uncertainty,[11][7] which gives Kalliope anaxial tilt of 103°. Kalliope's rotation is then slightly retrograde.
Between 2004 and 2021, 22 Kalliope has been observed tooccult fifteen stars.
In 2022, it was discovered that 22 Kalliope is part of anasteroid family that formed about 900 million years ago. Its moon, Linus, may have been formed at the same time.[12]
Kalliope has one known natural satellite, designated(22) Kalliope I and namedLinus. 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 byJean-Luc Margot andMichael E. Brown, while another team led by William Merline also independently detected the moon 3 days later.[6][7]
On 7 November 2006, the first stellar occultation by the satellite of an asteroid (Linus) was successfully observed by a group of Japanese observers[4] according to a prediction that was made just one day before by Berthier et al.[13] based on more than 5 years of regular observations of Kalliope binary system usingadaptive optics systems on ground-based telescopes. The observedchords of Linus give a unique opportunity to estimate the size of the moonlet which was estimated to 20–28 km.
