ASTRONOMY PICTURE

OF THE DAY

JUNE 23, 2011

Stereo Helene

EXPLANATION

Get out your red/blue glasses and float next to Helene, small, icy moon of Saturn. Appropriately named, Helene is one of four known Trojan moons, so called because it orbits at a Lagrange point. A Lagrange point is a gravitationally stable position near two massive bodies, in this case Saturn and larger moon Dione. In fact, irregularly shaped ( about 36 by 32 by 30 kilometers) Helene orbits at Dione’s leading Lagrange point while brotherly ice moon Polydeuces follows at Dione’s trailing Lagrange point. The sharp stereo anaglyph was constructed from two Cassini images (N00172886, N00172892) captured during the recent close flyby. It shows part of the Saturn-facing hemisphere of Helene mottled with craters and gully-like features.

Credit

Cassini Imaging Team, ISS, JPL, ESA, NASA; Stereo Image by Roberto Beltramini