¡SkyCaramba! Weekly astronomy blog for the week ending May 23, 2015
Saturn is at opposition on the 23rd. That means it’s at a point just about opposite the sun in the sky. It will rise as the sun goes down and set as the sun comes up. Oppositions happen when the sun, the earth, and the planet (or other object) at opposition line up with the earth between the other two.
The geometry that puts a planet at opposition also puts it at its minimum distance from Earth for the current orbit. In Saturn’s case, that distance is about nine astronomical units. An astronomical unit is one average earth-sun separation distance. So the ringed planet is nine times as far from us as we are from the sun this weekend.
Saturn orbits the sun in a little less than 29½ years. So when Earth has gone all the way around the sun, Saturn has moved through only about 3.4% of its orbit. That’s enough of a difference that when Earth gets to the same point in its orbit, it’s not between the sun and Saturn again. But it’s a small enough difference that it takes only 12 or 13 more ...