Space Topics: Saturn
Helene (S/1980 S6)
Running Ahead of Dione
Cassini passed within 36,000 kilometers of Helene to take this image on July
20, 2007. Helene is the leading co-orbital companion to Dione and is a small,
irregular body measuring approximately 36 by 32 by 30 kilometers in size. This
image has been enlarged by a factor of two. Credit: NASA / JPL / SSI |
Size: Irregular, 36 x 32 x 30 kilometers
Orbital radius: 377,400 kilometers - 6.26 Saturn radii - within
the E ring - at Dione’s leading Lagrange point (L4) - co-orbital with
Dione and Polydeuces
Orbital period: 2.7369 days - about 1/6 of Titan’s
Discovery: 1980 by P. Laques and J. Lecacheus
Helene is a tiny moon that orbits in Dione's leading Lagrange point (L4).
That is, Helene orbits Saturn on the same circular path that Dione does,
but ahead of Dione, and the centers of Dione, Saturn, and Helene form an
equilateral triangle.
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Voyager mission's best view of Helene
Voyager 2 captured this image of Helene on August 25, 1981, from a
distance of about 341,000 kilometers. Credit: NASA / JPL |
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Helene in day and night
These images were taken by Cassini on August 16, 2006 from a distance of
about 50,000 kilometers. The moonlet was lit at a high phase angle so only a
crescent is lit by the Sun. Both views are made from the same set of images.
The one on the left shows the sunlit crescent, while the one on the right shows
details on the night side visible in yellowish Saturnshine. Credit: NASA / JPL
/ SSI / Color by Gordan Ugarkovic
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Crossed-eye stereo image of Helene
Cassini captured these two images of Helene at slightly different times on July 20, 2007. Since Cassini's point of view shifted in the time between the two images, they can be used to create a 3-D view.
Credit: NASA / JPL / SSI / Stereo by Phil Stooke
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