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Fraser
2005-May-11, 04:58 PM
SUMMARY: Cassini has confirmed the discovery of a previously unseen moon tucked in a gap in Saturn's A ring. The moon, provisionally called S/2005 S1 for now, is only 7 km (4 miles) across, and orbits within the Keeler gap. Even though it's so small, you can clearly see the effect of its gravity on the nearby ring edge, which has distinctive waves along its edge. The is the second moon ever discovered within Saturn's rings. The first, Pan, is 25 km (16 miles) across and orbits within the Encke gap. All the other moons are outside the ring system.

View full article (http://www.universetoday.com/am/publish/new_moon_saturn_waves.html)

What do you think about this story? Post your comments below.

om@umr.edu
2005-May-11, 05:14 PM
This "moon" is noteworthy for its small size.

How small can an object be and still be classified as a "moon"?

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2005-May-11, 05:40 PM
Originally posted by om@umr.edu@May 11 2005, 05:14 PM
How small can an object be and still be classified as a "moon"?

That is a good question. As it is, this object may be larger than Mars' moon Deimos, but the question remains, is an orbiting 5 gram pebble a moon? I suspect the answer is that we will eventually constrain our language, but that for now, the pebble would be called a moon. Lucky thing we haven't discovered any, so the issue is still philosophical with no precident to follow.

aeolus
2005-May-11, 09:16 PM
Do we know if this can be called a "sheppard moon" that keeps the rings in order, or is this a dumb question? Are all the moons that are this close to the rings sheppard moons just by their nature of being a greater source of gravity acting on anything in the vicinity?