22 Kalliope
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22 Kalliope (Template:IPAc-en; Template:Respell) 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.
Characteristics
Kalliope is somewhat elongated, approximately 166 km in diameter,<ref name=Descamps2008/> 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 th
an that calculated from IRAS observations.<ref name="Descamps2008" />
The spectrum of Kalliope is an M-type, indicating that its surface may be partially composed of iron–nickel metal. The asteroid's density is about 3.4 g/cm3.<ref name=Descamps2008/> 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.<ref name=Descamps2008/> Spectroscopic studies have shown, however, evidence of hydrated minerals<ref name="Rivkin00">Template:Cite journal</ref> and silicates,<ref name="Lupishko82">Template:Cite journal</ref> which indicate rather a stony surface composition. Kalliope also has a low radar albedo,<ref name="Margot03"/> 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,<ref name="Kaasalainen02">Template:Cite journal</ref><ref name="Marchis03"/> which gives Kalliope an axial tilt of 103°. Kalliope's rotation is then slightly retrograde.
Between 2004 and 2021, 22 Kalliope has been observed to occult fifteen stars.
In 2022, it was discovered that 22 Kalliope is part of an asteroid family that formed about 900 million years ago. Its moon, Linus, may have been formed at the same time.<ref>Template:Cite journal</ref>
Satellite
Kalliope has one known natural satellite, designated (22) Kalliope I and named Linus. It is quite largeTemplate:Snd about 28 km in diameterTemplate:Snd 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.<ref name=Descamps2008>Template:Cite journal</ref> 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.<ref name="Margot03">Template:Cite journal</ref><ref name="Marchis03">Template:Cite journal</ref>
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<ref name="Soma06">Template:Cite journal</ref> according to a prediction that was made just one day before by Berthier et al.<ref name="Berthier04">Template:Cite journal</ref> 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.
Notes
References
External links
- Lightcurve plot of 22 Kalliope, Palmer Divide Observatory, B. D. Warner (2007)
- orbit diagram for Linus
- A different VLT image of Kalliope and Linus
- (22) Kalliope, datasheet, johnstonsarchive.net
- Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
- [1], Prediction and Reduction of Stellar Occultations of Binary Asteroids
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