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Friday, June 23

Planetary Moon "Mutual Events" as seen from Earth

If you have been following Chris' posts on the dance of Saturn's Moons as seen from Cassini, you might be wondering if the moons ever appear to cross (an occulation) or cast a shadow on each other (an eclipse) as viewed from Earth. The answer is yes. Every 15 years or so the plane of the Saturnian system lines up so that we see it side on. The rings almast disappear and a series of what are known as "mutual events" occur between the various moons of Saturn. This last took place in 1995/6 and will happen again in 2010.


Similar mutual event sequences take place for other planets. The interval is every 6 years for the Jovian system (Here are a couple of examples from my image archive taken in 2002 here and here) The next series is due around 2009


Much rarer are mutual events in the Uranian system which only happen every 42 years. The season however starts now and will continue for the next few years. Go to the Armagh Observatory website for more information.

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