Erinome (Jupiter XXV): an irregular, retrograde moon of Jupiter

Physical and orbital characteristics

Erinome is estimated to be roughly 3.2 kilometres in diameter. Its orbit around Jupiter is distant and elongated: the mean orbital radius is about 22,986,000 kilometres and the orbital period is approximately 711.965 days. The inclination of Erinome's orbit is steep and retrograde, about 164° to the ecliptic (roughly 162° relative to Jupiter's equator), and its orbital eccentricity is about 0.2552. These traits classify it as an irregular satellite rather than a regular, equatorial moon.

Key parameters at discovery and subsequent tracking include:

• Diameter: ~3.2 km
• Semi-major axis (average distance): ~22,986,000 km
• Orbital period: ~711.965 days
• Inclination: ~164° to the ecliptic
• Eccentricity: ~0.2552

Discovery and naming

Erinome was discovered in the year 2000 by a team of astronomers from the University of Hawaii led by Scott S. Sheppard. The object received the provisional designation S/2000 J 4 following its detection. After follow-up observations confirmed its orbit, the International Astronomical Union assigned the permanent Roman numeral designation Jupiter XXV and the name Erinome in October 2002, drawn from Roman mythology in which Erinome is associated as a lover of Jupiter.

Primary discovery and follow-up work are associated with professional surveys and observers; for more on the discovery team and observing programs see the University of Hawaii group and materials by Scott S. Sheppard. Additional context about designations is available via the announcement notices linked at discovery circulars.

Group membership and origin

Erinome is a member of the Carme group, a collection of irregular, retrograde moons that orbit Jupiter at similar distances and inclinations. The Carme group typically lies between about 23,000,000 and 24,000,000 km from Jupiter and has an inclination near 165°. Members of this group share similar orbital elements, which suggests a common origin, most likely the fragmentation of a single captured progenitor body.

Characteristics of the Carme group and evidence for a collisional origin can be explored further in resources about irregular satellites and group dynamics: Carme group overview, general classification notes at irregular satellite entries, and orbital data records at ecliptic/inclination summaries and eccentricity catalogs.

Scientific importance and notable facts

Although Erinome is small, studying moons like it helps astronomers understand the capture and collisional history of the Jovian system and the population of small, dark bodies in the outer Solar System. Because Erinome and its Carme-group companions share similar orbits, they serve as natural laboratories for researching how gravitational interactions, collisions, and tidal forces shape populations of irregular satellites.

For observational records, naming history, and additional technical details see the relevant notices and databases linked here: naming announcement, mythological background at Roman mythology, and discovery notes at satellite catalogs. Further ephemerides and dynamical studies are available through professional archives referenced at researcher pages and observatory logs.

Observing Erinome

Erinome is too faint for amateur telescopes and requires large professional telescopes and long-exposure imaging to detect and track. Its small size and dark surface make photometric or spectroscopic studies challenging, but comparisons with other Carme-group members allow inferences about composition and surface properties. For technical observation data and planning, consult the ephemerides and discovery papers at orbital element lists and survey summaries at mission archives.