The Half-Astrophysicist Blog

Saturn, the Rings, and the 61st Moon

The Cassinin spacecraft at Saturn continues to do remarkable work.  Today they announced the discovery of a small “moonlet” inside Saturn’s G ring.  The G ring is one of the outer rings, very thin and dusty.  The G ring was also an oddball since it was the only one of the dusty rings not to be affiliated with a moon…until now.  Here are the discovery images (click to embiggen).

A new moon in Saturns G Ring.

A new moon in Saturn's G Ring. Image Credit NASA/JPL/Space Science Institute

The Moon is shedding material which makes a nice bright arc near the moon.  That arc is about 150,000km (90,ooo miles) long or about one sixth the circumference of the circle.  The moon is too small to see directly, only about 500 meters (1/3 of a mile) across.  These images are 46 second exposures, so you can see the moon as a small streak (the other streaks are stars.  You can see how much the moon and stars moved in 46 seconds.  The camera tracked the rings so the rings would appear to stay still in the photos).  For the record, Cassini took this image from a distance of about 1.2 million km.

Although it is very small, so small they sometimes call it a moonlet, it is a source of material for the G ring.  But it might not be the only one.  There is evidence other objects up to 100 meters across may reside in the G ring.  Cassini will be making a close pass in 2010 so stay tuned for more.

March 3, 2009 - Posted by | Astronomy, Solar System

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