Learning about Helene

Admission time: I never heard of the Saturn moon Helene before. When pictures (such as a couple shown here) showed up, I had to investigate. Helene is a little moon (a moonlet? a moonitesimal? a dwarf moon?) that happens to be in a stable Lagrange point with the larger Dione. So (as many have already noted), Helene is a Saturnian Trojan moon, where the Trojans stand for the asteroids that are clustered around Jupiter's stable Lagrange point. Earth has a few asteroids in the Trojan positions, the stable Lagrange points, too. So with regard to Helene, she's boxed (reference: Boxing Helena, picture) in a Trojan location around Saturn, and is thus Helene of Troy. (And it really was named after the fabulous Helen, who apparently by virtue of being descended from a god, gets to be a goddess, even though she was human.)

[Which brings up the question, who was the more beauteous recent cinematic Helen: Diane Kruger or Sienna Guillory?]

I had heard of stable Lagrange points -- they are points in the orbit that are gravitically balanced between a large orbiting object, the much larger object that is being orbited around, and the location of the points. So stuff tends to accumulate there. Given all the gravitic pulls and tugs in multi-body systems, it seems amazing that there are stable points, but apparently there are.

So anyway, Helene is a little irregularly-shaped moon, which doesn't do much except orbit Saturn, stay out of Dione's way, and get featured on lists of Saturnian moons. Helene was discovered in 1980, by the way.

Another picture of Helene

Helene info from SolarViews

Close-up of Helene

Fly-by report

More on Helene, and Calypso (another Saturn Trojan, in the link) and Lagrange points