Sinope (moon of Jupiter)

Physical and orbital characteristics

Sinope is relatively small, with a size on the order of tens of kilometres across, and lacks a spherical form. Its orbit is retrograde, meaning it travels around Jupiter in the opposite direction to the planet's rotation. The orbit is both tilted and elongated compared with Jupiter's regular moons, and it takes many months to complete a single revolution. Its surface appears relatively red in color, a trait that has been used to infer links to particular types of primitive asteroidal material.

Discovery and naming

The moon was discovered in 1914 by astronomer Seth B. Nicholson at Lick Observatory. Early designations treated it numerically as one of Jupiter's satellites; it was commonly called Jupiter IX for many decades. Between 1955 and 1975 it was sometimes referred to informally as "Hades." The official name Sinope, drawn from a figure in Greek mythology, was adopted in 1975. More on the discovery can be found in archival resources at Lick Observatory records, while naming conventions are discussed in historical catalogs at classical name references.

Origin and group associations

Sinope is often associated with the Pasiphae group, a collection of distant, retrograde Jovian moons that likely share a common origin after the capture and fragmentation of a parent body. However, Sinope's orbital parameters and spectral properties differ enough from some members of that group that astronomers debate whether it is truly a fragment of the same collision or a separately captured object. Studies of composition and dynamics are available through planetary data archives and survey results at relevant observational databases.

Observational history and significance

For much of the 20th century Sinope was one of Jupiter's most distant-known satellites. It remained the outermost known moon until surveys around the year 2000 found additional small, distant satellites such as Megaclite and others; more recent discoveries have extended the known family of outer Jovian moons even farther from the planet. Basic orbital elements and comparative analyses of distant Jovian moons are summarized in technical listings and survey reports found at survey summaries and nomenclature and catalog pages.

Although small and faint, Sinope helps astronomers understand the population of captured bodies around giant planets, the dynamics of irregular satellites, and the collisional history of the outer Jovian system. Continued telescopic study refines its orbit and surface properties and informs models of how Jupiter acquired its diverse entourage of moons.