22 Kalliope (; ) is a large

M-type asteroid M-type (metallic-type, aka M-class) asteroids are a spectral class of asteroids which appear to contain higher concentrations of metal phases (e.g. iron-nickel) than other asteroid classes, and are widely thought to be the source of iron meteorit ...

from the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

discovered by J. R. Hind on 16 November 1852. It is named after

Calliope In Greek mythology, Calliope ( ; ) is the Muse who presides over eloquence and epic poetry; so called from the ecstatic harmony of her voice. Hesiod and Ovid called her the "Chief of all Muses". Mythology Calliope had two famous sons, OrpheusH ...

, the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

Muse In ancient Greek religion and Greek mythology, mythology, the Muses (, ) were the Artistic inspiration, inspirational goddesses of literature, science, and the arts. They were considered the source of the knowledge embodied in the poetry, lyric p ...

epic poetry In poetry, an epic is a lengthy narrative poem typically about the extraordinary deeds of extraordinary characters who, in dealings with gods or other superhuman forces, gave shape to the mortal universe for their descendants. With regard t ...

. It is orbited by a small moon named Linus.

Characteristics

Kalliope is somewhat elongated, approximately 166 km in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

, and slightly asymmetric, as evidenced by resolved images taken with the VLT at the

European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 m ...

. This new diameter, which was measured by observing mutual eclipses of Kalliope and Linus, is 8% smaller than that calculated from

IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...

observations. The spectrum of Kalliope is an M-type, indicating that its surface may be partially composed of

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

–

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

metal. The asteroid's density is about 3.4 g/cm³. Since the asteroid is likely to be a

rubble pile In astronomy, a rubble pile is a celestial body that consists of numerous pieces of debris that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the various chunks that make the ...

, 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

silicate A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used ...

s. Spectroscopic studies have shown, however, evidence of

hydrated In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

minerals and silicates, which indicate rather a stony surface composition. Kalliope also has a low radar albedo, which is inconsistent with a purely metallic surface. Lightcurve analysis indicates that Kalliope's pole most likely points towards

ecliptic coordinates In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small So ...

(β, λ) = (−23°, 20°) with a 10° uncertainty, which gives Kalliope an

axial tilt In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbita ...

of 103°. Kalliope's rotation is then slightly retrograde. Between 2004 and 2021, 22 Kalliope has been observed to

occult The occult () is a category of esoteric or supernatural beliefs and practices which generally fall outside the scope of organized religion and science, encompassing phenomena involving a 'hidden' or 'secret' agency, such as magic and mysti ...

fifteen stars. In 2022, it was discovered that 22 Kalliope is part of an

asteroid family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An ...

that formed about 900 million years ago. Its moon, Linus, may have been formed at the same time.

Satellite

Kalliope has one known natural satellite, designated (22) Kalliope I and named Linus. 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. Linus was discovered on 29 August 2001 by

Jean-Luc Margot Jean-Luc Margot (born 1969) is a Belgian-born astronomer and a UCLA professor with expertise in planetary sciences and SETI. Career Margot has discovered and studied several binary asteroids with radar and optical telescopes. His discoveries ...

and

Michael E. Brown Michael E. "Mike" Brown (born June 5, 1965) is an American astronomer, who has been professor of planetary astronomy at the California Institute of Technology (Caltech) since 2003. His team has discovered many trans-Neptunian objects (TNOs), ...

, while another team led by William Merline also independently detected the moon 3 days later.

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 according to a prediction that was made just one day before by Berthier et al. based on more than 5 years of regular observations of Kalliope binary system using

adaptive optics Adaptive optics (AO) is a technique of precisely deforming a mirror in order to compensate for light distortion. It is used in Astronomy, astronomical telescopes and laser communication systems to remove the effects of Astronomical seeing, atmo ...

systems on ground-based telescopes. The observed

chords Chord or chords may refer to: Art and music * Chord (music), an aggregate of musical pitches sounded simultaneously ** Guitar chord, a chord played on a guitar, which has a particular tuning * The Chords (British band), 1970s British mod ...

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

datasheet, johnstonsarchive.net

Robert Johnston, johnstonsarchive.net

Prediction and Reduction of Stellar Occultations of Binary Asteroids * * {{DEFAULTSORT:000022 Background asteroids

Kalliope In Greek mythology, Calliope ( ; ) is the Muse who presides over eloquence and epic poetry; so called from the ecstatic harmony of her voice. Hesiod and Ovid called her the "Chief of all Muses". Mythology Calliope had two famous sons, OrpheusH ...

Binary asteroids M-type asteroids (Tholen) X-type asteroids (SMASS) 18521116