March 30, 2020

Astro-Challenge: See Saturnís Moons in 1 to 7 Order.

This weekís challenge may also give you a unique photographic opportunity. On the evening of July 31st (my birthday!) Saturnís moons will be in 1 to 7 order. This will occur from 6:45 to 11:15 Universal Time, and favor viewers in Australia and the Far East. Later in the†evening over North America, only speedy Mimas and Enceladus will be out of orderÖ now is the time to brush up on and perhaps nab some of those hard to spot moons; in descending magnitude, difficulty, and order number (#) †they are:

Titan +8.6(6), Rhea +10(5),Tethys +10.5(3), Dione +10.7(4), Enceladus +12(2), Mimas +13(1), and Hyperion at <+13(7). Needless to say, Hyperion and Mimas are the most difficult of the bunch. All moons will appear in a tight clustering to the eastward side of the planet; only leisurely Iapetus(8) will be off to the west. There is no†observable 1 through 8 configuration for the year of 2010. Remaining alignments of Saturnís moons for 2010 are as follows;

1 TO 7 IN ORDER ON JUL 31 1045 TO 1515 (2 TO 6 IN A SMALL SCOPE)
1 TO 6 IN ORDER ON AUG 24 0815 TO 1030 (2 TO 6 IN A SMALL SCOPE)

1 TO 5 IN ORDER ON OCT 18 0015 TO 0500
1 TO 5 IN ORDER ON OCT 24 1045 TO 1130
1 TO 5 IN ORDER ON OCT 30 0100 TO 0315
1 TO 5 IN ORDER ON DEC 11 2145 TO 2345

And donít forget to check out the planets Mars and Venus, which now form a nice triangle with Saturn. Our thanks to reader Ed Kotapish, who passed on the calculations for this interesting event.

The Astroword for this week is the Cassini Gap. Also sometimes known as the Cassini Division, this is the most prominent gap in Saturnís rings and is easily visible with a small telescope. First noted by Christiaan Huygens in 1655, the Voyager spacecraft revealed that there are in fact thousands of lesser gaps is Saturnís rings, resembling the grooves in a record. The Cassini Gap isnít entirely devoid of ring material; it is however in a strong orbital resonance with the moon Mimas which completes one orbit per every two for particles in the division. Saturnís rings are just starting to open up from being edge on last year in respect to our Earthly vantage point, and the Cassini Gap is just starting to become visible again with a small telescope. An interesting challenge is to try and spy the limb of Saturn through the division; this will become easier to do once Saturnís rings are at their maximum observed opening around 2017.

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