Dione's Lagrange Moon Helene
Explanation:
Saturn's moon
Helene
is very unusual in that it circles
Saturn near the
orbit of a bigger moon:
Dione.
Helene is situated in what is called a
"Lagrange point" of Dione - a place of stability created by Dione's
gravity. Were
Helene to stray slightly from its orbit 1/6 ahead of Dione,
the larger moon's gravity would cause Helene to move back toward the
Lagrange point. Many massive orbital bodies have stable Lagrange points,
including the Earth and Moon. Helene was discovered from the ground by P.
Laques & J. Lecacheux in 1980. The photograph above was taken by Voyager 2
as it passed Saturn in 1981. NASA's
Cassini
mission to Saturn is currently
scheduled for launch in October 1997.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
