Kallichore (moon)

on 6 February 2003 Kallichore was discovered by Scott S. Sheppard on 6 February 2003, during a search for distant moons of Jupiter at Mauna Kea Observatory in Hawaii. Conducted in collaboration with David Jewitt, the search involved routine imaging of the sky near Jupiter using various large telescopes equipped with sensitive digital cameras. Sheppard made the discovery observations of Kallichore using the Canada–France–Hawaii Telescope, while Brian G. Marsden computed the orbit of Kallichore from Sheppard's observational data. The discovery of Kallichore, together with S/2003 J 9, S/2003 J 10, and S/2003 J 12, was announced by the Minor Planet Center and Central Bureau of Astronomical Telegrams on 7 March 2003. Kallichore was one of the 21 Jovian moons announced in 2003, which raised Jupiter's known moon count to 61 in that year. == Name ==

When the discovery of Kallichore was announced, it was given the temporary provisional designation . The moon was officially named "Kallichore" with the Roman numeral designation () by the International Astronomical Union's (IAU's) Working Group for Planetary System Nomenclature on 30 March 2005. The moon's name comes from Callichore, one of the Muses and one of Zeus's daughters in Greek mythology. The name follows the IAU's naming convention for Jovian moons, which are named after mythological lovers and descendants of Zeus or Jupiter. Since Kallichore has a retrograde orbit, it was given a name ending with the letter "e". == Orbit ==

Kallichore is an irregular moon of Jupiter, meaning it follows a very wide, inclined, and eccentric orbit around the planet. The orbit of Kallichore is retrograde, meaning it orbits in the opposite direction to Jupiter's rotation. The moon orbits Jupiter at an average distance of , which places it far beyond the Galilean moons. Like all other irregular moons of Jupiter, Kallichore orbits far enough that its orbit is strongly influenced by gravitational perturbations by the Sun and other giant planets, which causes frequent changes in its orbit. As a result, Kallichore's orbit does not form a closed ellipse. Proper (or mean) orbital elements are often used to describe the general shape and orientation of the orbits of irregular moons like Kallichore. On average, Kallichore has an orbital period of about with an orbital eccentricity of 0.259 and an inclination of 164.6° with respect to the ecliptic. Simulations over a 1,000-year timescale show that Kallichore's orbital semi-major axis varies from , while Kallichore's eccentricity and inclination vary from 0.113 to 0.413 and 160.8° to 167.8°, respectively. Kallichore's orbit exhibits nodal and apsidal precession with periods of 86.3 and 49.1 years, respectively. A 2011 study by Julien Frouard and colleagues found that Kallichore's orbit appears to be influenced by a secular resonance involving the nodal and apsidal precession frequencies of itself, Saturn, Uranus, and Neptune.{{efn|Frouard et al. (2011) describe Kallichore's secular resonance as a " year libration of the angle s + 10\nu_{GI} + 4g_6 + 4s_7 + 20s_8 + s_6", where s is Kallichore's nodal precession frequency, \nu_{GI} = 2n_5 - 5n_6 = -1467 \text{ arcsec/yr} is the "Great Inequality" between the mean motions (orbital frequency n) of Jupiter (subscript 5) and Saturn (subscript 6), g_6 is the apsidal precession frequency of Saturn, s_7 is the nodal precession frequency of Uranus, s_8 is the nodal precession frequency of Neptune, and s_6 is the nodal precession frequency of Saturn.}} File:Kallichore orbit oblique view.svg|Oblique view of Kallichore's orbit (red), with the Galilean moons (magenta) and other irregular moons of Jupiter (gray) plotted File:Kallichore orbit side view.svg|Side view of Kallichore's orbit (red), with the Galilean moons (magenta) and other irregular moons of Jupiter (gray) plotted File:Kallichore orbit top view.svg|Top view of Kallichore's orbit (red), with the Galilean moons (magenta) and other irregular moons of Jupiter (gray) plotted Group membership and origin Kallichore shares similar orbital characteristics as Jupiter's large irregular moon Carme, which makes it a member of the Carme group. The moons of the Carme group are believed to be fragments of a larger body that was gravitationally captured by Jupiter and destroyed by a collision several billion years ago. Based on the known colors and compositions of moons from the Carme group, the group's parent body likely originated from the outer Solar System, either as a D-type asteroid from the Hilda or Jupiter trojan populations or from the centaur and trans-Neptunian object populations. == Physical characteristics ==

on 15 December 2025. Kallichore's position is indicated by the black circle (with gray circles representing possible alternative sizes and positions for Kallichore) in the empty gap between the colored chords (representing observations of the star occulted by Kallichore). Due to its small size, Kallichore appears very faint from Earth with a visual apparent magnitude of around 23, so it could only be observed by very large, sensitive telescopes. Observations of a stellar occultation from 2025 show that Kallichore is between and in diameter, which suggests it has a dark surface with a geometric albedo of around . Kallichore is expected to share similar properties as other moons of the Carme group, such as their slightly reddish surface colors (V–R 0.47), organic-rich surface compositions, and low albedos of around 4%. Kallichore may additionally contain water ice, though most of it is expected to be buried beneath a layer of dark, refractory material. Kallichore is irregularly shaped because it is too small for its gravity to pull itself into a sphere. The Hubble Space Telescope has observed changes in Kallichore's brightness (magnitude change of Δm ≥ ) within 1.25 hours, which suggests the moon has a moderately elongated shape with a minimum semi-axis ratio of a/b ≥ . This elongated shape is expected for a kilometer-sized body that has been shaped by collisions. Since Kallichore is thought to have been shaped by collisions, it is suspected to have a rubble pile interior structure, similar to those of the kilometer-sized asteroids 162173 Ryugu and 101955 Bennu. The rotation period of Kallichore is unknown because its brightness changes have not been observed long enough. == Potential exploration ==

Kallichore has been identified as a potential flyby target for the European Space Agency's Jupiter Icy Moons Explorer (Juice) mission, which is predicted to pass closer than from the moon on 7 October 2031, during the spacecraft's first orbit around Jupiter. A 2026 study by Arnaud Boutonnet and Amedeo Rocchi determined that the Juice spacecraft could come even closer to Kallichore if it expended at least of delta-v (Δv) during its energy reduction phase (or pump-down sequence) after entering orbital insertion around Jupiter. In order for Juices highest resolution camera (JANUS) to resolve Kallichore beyond one pixel, the spacecraft must come within of the moon. One possible trajectory could bring Juice as close as from Kallichore on 5 October 2031; this flyby would occur near Juices apojove (farthest point from Jupiter) and the spacecraft would approach Kallichore from its unilluminated side (phase angle ~145°). A flyby this close would allow Juice to resolve Kallichore's shape and surface features. However, , Kallichore is predicted to have a large positional uncertainty of ± on the date of Juices expected flyby. Before a decision can be made to direct Juice closer to Kallichore, the moon's positional uncertainty on the flyby date must be reduced to less than ± by 2028. Further observations of Kallichore are planned to accurately determine its orbital path. Preparation Beginning in 2025, astronomers on behalf of the Juice mission team began conducting a series of astrometric observations to better determine Kallichore's orbital path. Kallichore was imaged by the Hubble Space Telescope on 30 November and 4 December 2025, which refined Kallichore's orbit enough to facilitate the prediction of a stellar occultation by the moon on 15 December 2025. Kallichore's December 2025 occultation was successfully detected by three telescopes in Italy, alongside ten non-detections from Europe and the United States, which altogether significantly constrained Kallichore's size and position. These observations make Kallichore the smallest irregular moon observed by stellar occultation . Kallichore was further imaged by the Gran Telescopio Canarias on 21–22 January 2026. From November 2025 to February 2026, Kallichore's positional uncertainty on the expected Juice flyby date had dropped from . Another stellar occultation by Kallichore was predicted to occur over Australia on 18 March 2026. A campaign for observing this occultation was organized by the Instituto de Astrofísica de Andalucía. The campaign aimed to further constrain Kallichore's shape and position. == See also ==