William Atkins
Tuesday, 22 September 2009 19:19
Science -
Space
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The scene opened up on August 11, 2009, when light from the Sun was directed exactly edge-on to Saturn’s rings.
It was equinox for the planet, when the Sun crosses the equator of the planet at either of two times during its annual trip around the Sun.
On Earth, we call these times the beginning of spring and autumn, when the days and nights are approximately equal and we name it the vernal (spring) equinox and the autumnal (fall) equinox.
In fact, people in the Northern Hemisphere are about to have their fall equinox on September 22, while people in the Southern Hemisphere are preparing themselves for their spring equinox. These events happen every six months, or twice every year, as Earth travels around the Sun in its orbit that takes about 365 days to complete.
In the case of Saturn, this equinox event happens twice during Saturn’s trip around the Sun, which takes about 10,759 Earth-days, or about 29.7 Earth-years.
During the equinox event at Saturn (which only happens every 14.85 Earth-years or so), the Cassini team took advantage of the event for their discovery. The main rings of Saturn are known as A, B, C, and D.
Their thickness had previously thought to have been only about 30 feet (nine meters). However, images from Cassini found that the height of the rings were as high as 2.5 miles (about four kilometers).
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