Janus

Janus is a Saturnian moon that shares an orbit with Epimetheus.[2] Janus also bears the designations Saturn X and S/1980 S1.[2] JPL lists Janus's mean radius as 89.2 kilometres.[1]

History

Audouin Dollfus observed Janus on December 15, 1966.[2] Voyager 1 verified the two-moon arrangement in 1980.[2]

Findings

Roughly every four years, the moons switch between the inner and outer tracks.[2] The two moons pass within about 15,000 kilometres of one another.[2] Each orbit around Saturn takes them about 17 hours.[2] The ESA table lists its dimensions as 154 by 194 kilometres.[3]

Sources

  1. Solar System Dynamics: Physical Parameters. Licence: facts-only (Track B), no text reused. Attribution: NASA/JPL-Caltech.
  2. Janus | NASA Science. Licence: facts-only (Track B), no text or images reused. Attribution: NASA.
  3. Saturn's moons | ESA. Licence: facts-only (Track B), no text reused. Attribution: European Space Agency.

Evidence as of 2026-11-01.