Kallichore (moon)
A small irregular moon of Jupiter and potential Juice flyby target.
Kallichore (Jupiter XLIV, formerly S/2003 J 11) is a tiny moon of Jupiter, measuring about 4 km (2.5 mi) across and shaped like an elongated object. It belongs to the planet’s irregular moons, which travel in wide, tilted, and stretched-out orbits far from Jupiter. Discovered by Scott S. Sheppard on February 6, 2003, using the 3.6-meter Canada–France–Hawaii Telescope at Mauna Kea Observatory, its orbit was calculated by Brian G. Marsden. The discovery, along with three other moons, was announced on March 7, 2003, and Kallichore was one of 21 Jovian moons reported that year, bringing Jupiter’s known count to 61.
The moon was officially named by the International Astronomical Union on March 30, 2005, after Callichore, a Muse and daughter of Zeus in Greek mythology. Its name ends with “e” because it orbits in a retrograde direction—opposite to Jupiter’s rotation. Kallichore circles Jupiter at an average distance of 23.0 million km (14.3 million mi), taking about 714 days (1.95 years) per orbit, with an eccentricity of 0.259 and an inclination of 164.6° relative to the ecliptic. Its orbit is strongly affected by the Sun and other giant planets, so it doesn’t form a closed ellipse; over 1,000 years, its semi-major axis varies between 22.0 and 24.4 million km, its eccentricity between 0.113 and 0.413, and its inclination between 160.8° and 167.8°. The orbit also shows nodal and apsidal precession cycles of 86.3 and 49.1 years, and a 2011 study found it may be influenced by a secular resonance involving Saturn, Uranus, and Neptune.
Kallichore shares similar orbital traits with Jupiter’s larger irregular moon Carme, placing it in the Carme group. These moons are thought to be fragments of a larger body—likely a D-type asteroid from the Hilda or Jupiter trojan populations, or a centaur or trans-Neptunian object—that was captured by Jupiter and shattered by a collision billions of years ago. Physically, Kallichore is very faint (apparent magnitude around 23) and only visible with large telescopes. A 2025 stellar occultation showed its diameter ranges from 3.5 to 6.1 km, and its dark surface has a geometric albedo of about 3.7% (+0.7%/−2.2%). It likely shares the Carme group’s slightly reddish color (V–R = 0.47), organic-rich surface, and low albedo around 4%. Water ice may be present but buried under dark, refractory material.
Quick Facts
- Discovered
- 6 February 2003
- Discoverer
- Scott S. Sheppard
- Discovery Site
- Mauna Kea Obs.
- Mpc Name
- Jupiter XLIV (44)
- Pronounced
- k · ə · ˈ · l · ɪ · k · ɒ · r · iː
- Adjective
- Kallichorean ˌ · k · æ · l · ᵻ · k · ə · ˈ · r · iː · ə · n
- Named After
- Καλλιχόρη Kallichorē
- Observation Arc
- 2003 · 2021
- P Semimajor Unitless
- 23017100 km
- P Eccentricity
- 0.253
- P Inclination
- 164.7° (to ecliptic)
- P Period Unitless
- 713.59 d
Facts from the source article.
Lore & Background
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. The discovery was made using the 3.6-meter Canada–France–Hawaii Telescope, and Brian G. Marsden computed its orbit. The moon was given the temporary provisional designation S/2003 J 11 and was officially named 'Kallichore' with the Roman numeral designation Jupiter XLIV on 30 March 2005. The name comes from Callichore, one of the Muses and one of Zeus's daughters in Greek mythology.
Kallichore orbits Jupiter in the retrograde direction at an average distance of 23.0 million km. It shares similar orbital properties as Jupiter's larger irregular moon Carme, making it a member of the Carme group. The moons of the Carme group are believed to be fragments of an asteroid or trans-Neptunian object that was gravitationally captured by Jupiter and destroyed by a collision several billion years ago. Kallichore is an elongated object with a diameter of about 4 km, and its small size and low brightness suggest it has a dark surface with a geometric albedo of around 3.7%.
Reader's Guide
Kallichore's significance lies in its role as a potential flyby target for the European Space Agency's Juice mission, which is predicted to pass closer than 1 million km from the moon on 7 October 2031. A 2026 study determined that the Juice spacecraft could come even closer if it expended at least 23 m/s of delta-v during its energy reduction phase. One possible trajectory could bring Juice as close as 700 km from Kallichore on 5 October 2031, which would allow Juice to resolve the moon's shape and surface features. However, as of March 2026, Kallichore is predicted to have a large positional uncertainty of ±272 km on the flyby date. Before a decision can be made to direct Juice closer, the moon's positional uncertainty must be reduced to less than ±30 km by 2028. Beginning in 2025, astronomers began conducting astrometric observations to better determine Kallichore's orbital path, including imaging by the Hubble Space Telescope on 30 November and 4 December 2025. These observations facilitated the prediction of a stellar occultation on 15 December 2025, which was successfully detected by three telescopes in Italy, making Kallichore the smallest irregular moon observed by stellar occultation as of 2026.
Did You Know?
- It is a member of the Carme group, believed to be fragments of an asteroid or trans-Neptunian object captured by Jupiter.
- Kallichore is a potential flyby target for the Juice mission, predicted to pass closer than 1 million km on 7 October 2031.
- A stellar occultation in December 2025 made Kallichore the smallest irregular moon observed by occultation as of 2026.
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