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Encyclopedia > Saturn > Inner satellites V

JANUS AND EPIMETHEUS :  SATELLITES X AND XI OF SATURN,

"SHEPHERDS" OF THE RINGS


Credit : C. J. Hamilton/NASA

Janus (Saturn X) was discovered by the astronomer Audouin Dollfus in 1966. Its revolution period is 16 hours et 40 minutes.

Credit : Cassini/ESA/NASA

Epimetheus (Saturn XI) was discovered by Walker, Larson, and Fountain in 1978, which was confirmed by Voyager 1 in 1980. It rotates on the same orbit as Janus. Its revolution period is 16 hours and 40 minutes.



  
Janus: Epimetheus:
distance to Saturn in km 151 470 151 420
average size  176x194x154 km 119x138x110 km 
visual magnitude   14.5 18.5
revolution period 0.695 day 0.694 day
orbital velocity 16 km/s 15.87 km/s
inclination of the orbit 
on the equator of Saturn		 0.14° 0.34°
eccentricity of the orbit 0.007 0.009
escape velocity  52 m/s ?
reflectivity (geometric albedo) 0.8 ?

Opposite: the Voyager and Cassini images of the two satellites Janus and Epimetheus.

Origin of the names : click here.