Kallichore (moon)
Kallichore, also known as ' and previously as ', is a small natural satellite or moon of Jupiter. It is one of Jupiter's many irregular moons, which orbit far from the planet on highly inclined and elliptical orbits. Kallichore was discovered by Scott S. Sheppard on 6 February 2003 and was named after Callichore, one of Zeus's daughters in Greek mythology.
Kallichore has an estimated diameter between. It orbits Jupiter in the retrograde direction—opposite to the direction of the planet's rotation—at an average distance of. Kallichore shares similar orbital properties as Jupiter's larger irregular moon Carme, which makes it a member of the Carme group. The moons of the Carme group are believed to be fragments of an asteroid that was gravitationally captured by Jupiter and destroyed by a collision several billion years ago.
Kallichore is a potential flyby target for the European Space Agency's Jupiter Icy Moons Explorer mission, which is predicted to pass closer than from the moon in October 2031. Although it is possible for Juice to come even closer to Kallichore, this possibility remains under investigation.
Discovery
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 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 elliptical 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. For this reason, proper (or mean) orbital elements are often used to describe the general shape and orientation 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.
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 an asteroid that was gravitationally captured by Jupiter and destroyed by a collision several billion years ago. The parent body of the Carme group was probably a D-type asteroid that possibly originated from either the Hilda asteroid or Jupiter trojan populations.Physical characteristics
Little is known about Kallichore's physical characteristics. Like many of Jupiter's irregular moons, Kallichore is very faint with an average apparent magnitude of 23.7, so it is best observed with large, sensitive telescopes. Kallichore is expected to share similar properties as other moons of the Carme group, such as their slightly reddish surface colors and low albedos of around 0.04. Scott Sheppard and NASA estimate Kallichore to be in diameter, whereas Tilmann Denk estimates Kallichore to be in diameter. Kallichore is likely irregularly shaped because it is too small for its gravity to pull itself into a sphere.Potential exploration
Kallichore has been identified as a potential flyby target for the European Space Agency's Jupiter Icy Moons Explorer mission, which is predicted to pass closer than from the moon during the spacecraft's first orbit around Jupiter in October 2031. 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 during its energy reduction phase after entering orbital insertion around Jupiter. One possible trajectory could bring Juice as close as from Kallichore on 5 October 2031; this flyby would occur near Juices apojove and the spacecraft would approach Kallichore from its unilluminated side. A flyby this close would allow Juice to resolve Kallichore's shape and surface features.The option of adjusting Juices trajectory to fly closer to Kallichore remains under investigation by the Juice mission team. Additional observations of Kallichore were conducted in 2025 to refine planning for Juices potential flyby of Kallichore: these included observations by the Hubble Space Telescope and an observing campaign for a predicted stellar occultation by Kallichore on 15 December 2025.