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Saturn at Opposition II
StarDate:
July 20, 2020Every planet orbits the Sun in the same direction. If you viewed the solar system from above the Sun’s north pole, they’d all be moving counterclockwise.
But what we see doesn’t always reflect that. Right now, for example, the giant planets Jupiter and Saturn are moving backwards — a motion known as retrograde. That doesn’t mean the planets have reversed direction, though. Instead, it’s caused by Earth’s motion relative to the two planets.
Earth is closer to the Sun, so it moves faster in its orbit. Once every year or so, it passes Jupiter and Saturn. As it does so, they appear to move in reverse for a while. Instead of their usual eastward motion against the background of stars, they move westward for a while.
Think of driving down the highway. The cars that are well ahead of you appear to be moving forward against the background of buildings and trees. If you zoom past them, though, they briefly appear to move backward against the background. Then, as you pull away, they appear to resume their normal forward motion.
Saturn began the year in Capricornus. As Earth began overtaking the planet, though, it moved in reverse, into Sagittarius, where it is now. It’ll soon resume its forward motion, though, and be back in Capricornus in December.
Jupiter and Saturn are in the southeast as night falls. Jupiter looks like a brilliant star, with not-as-bright Saturn to its lower left. They’re in view all night long.
More tomorrow.
