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Although I like to mix it up in my monthly columns, Saturn is a subject to which I have no problem returning.
The main purpose of this column is to inform readers about sky subjects they can observe from their backyards, and Saturn tops the list. It is stunning, unmistakable and accessible with a pair of binoculars, and on April 15, Saturn will be at its closest point to Earth (opposition, where Earth is directly between it and the sun).
Throw even a small telescope into the mix and some observers literally won't believe their eyes. One of my neighbors once insisted I had inserted a photo into the end of my telescope to play a trick on her when she peered through the eyepiece at Saturn.
Like most planets, including Earth, Saturn's axis of rotation is tilted compared to its orbital plane. Relatively speaking, its poles do not face directly up and down. Saturn's axis is tilted almost 27 degrees while Earth's tilts about 23 degrees. Factoring in Saturn's tilt and where both planets are in their respective orbits indicates how Saturn and its rings will appear to earthbound observers.
Saturn's rings, which orbit Saturn directly at its equator and are therefore tilted along with the planet, are beginning to open up as Saturn takes its nearly 30-year trip around the sun. In 2009 and 2010 the rings faced Earth edge on, and now they're starting to tilt downward. In 2016 and 2017, they'll be at their most open, with the north side, or top, of the rings facing us, until they face us edge on again in 2024 and 2025. At that point, Saturn's north pole will begin to tilt away from us, exposing the bottom, or south side, of its rings.
Saturn's ring system has nine continuous main rings and three partial rings, or arcs. They are composed mostly of ice particles with some rocky debris and dust thrown in. The count of known moons orbiting the planet is at 62 - not including the hundreds of moonlets, or solid particles large enough to be considered moons, within the rings. Titan, Saturn's largest moon and the solar system's second largest after Jupiter's moon Ganymede, is larger than the planet Mercury and has its own atmosphere.
The rings extend 4,120 to 75,000 miles above Saturn's equator and average just 30 feet to a few miles in thickness. One theory about the formation of the rings states that they are remnants of a destroyed moon. Another theory is that the rings are left over from the original material that formed Saturn. Some of the ice in the central rings comes from the moon Enceladus' ice volcanoes. In the past, astronomers thought the rings formed with Saturn billions of years ago. Newer data indicates the rings are probably just a few hundred million years old.
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April 6 - Full moon.
April 15 - Saturn at opposition. The ringed planet will be at its closest approach to Earth. This is the best time to view and photograph Saturn and its moons.
April 21 - New moon.
April 21 and 22 - Lyrids meteor shower peaks. The Lyrids usually produce about 20 meteors an hour during peak. Because it coincides with the new moon, even faint meteors will be visible. Look for shooting stars radiating from the constellation Lyra after midnight.