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Planetary Satellites

What is a planetary satellite?

Naturally-formed bodies in orbit around planets are referred to here as “planetary satellites”, and are often called “moons.” Planetary satellites (as well as the primary planet) orbit the planetary system barycenter, the combined center of mass of the planet and all of the moons in that planetary system. The barycenter, in turn, orbits the Sun. The Sun, in turn, orbits the center of the Galaxy, an orbit which, as of yet, is not available on Horizons. The best-known planetary satellite is, of course, Earth’s moon, eponymously named — before any other planetary satellites were known — “the Moon”. Currently, we know of no planetary satellites in orbit around Mercury or Venus. All the other planets have at least one known planetary satellite.

Description of Menu Items

PageDescription
Orbits & EphemeridesProvides access to orbital data for all known planetary satellites.
Physical ParametersTable of selected physical parameters for planetary satellites.
Gravity FieldsVisualize and download the gravity fields of several planets, the moon, and a few small-bodies.
Observational DataProvides sets of observations that are currently being used in the creation and improvement of JPL's planetary satellite ephemerides.
Discovery CircumstancesDiscovery circumstances for known planetary satellites.