Thursday, June 25, 2009

Casini Snaps: Eclipse darkens 'Death Star' Moon

The Cassini probe has caught its first glimpse of one Saturn moon eclipsing another, as the moon Enceladus passed silently in front of its neighbour Mimas.

Most of Saturn's moons orbit in the same plane as its rings, along the planet's equator. This arrangement creates frequent alignments, but eclipses are rare because the sun must illuminate this plane almost edge-on in order for moon shadows to be cast in the right direction.

For the first time in almost 15 yearsMovie Camera, Saturn has reached a spot in its orbit where such events can be seen. The planet's rings, which are tilted by some 27°, will be illuminated perfectly edge-on during Saturn's equinox on 11 August 2009.

The visible moon in this series of images is Mimas, which resembles the Death Star, the planet-destroying space station from the movie Star Wars. It is eclipsed by Enceladus, which spews giant plumes of ice and water vapour from its south pole.

Cassini snapped the eclipse on 13 May, when the probe was roughly 1.3 million kilometres from Mimas.

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