dipper@utastro.UUCP (Debbie Byrd) (07/25/85)
The planet Saturn appears near the moon in tonight's sky. More -- after this. July 25 The Moon near Saturn It's easy to find the planet Saturn tonight. Look southward in the sky right after sunset. Saturn will be that bright golden point of light -- the closest bright object to the moon. Right now Saturn trails behind Earth in orbit around the sun. Saturn takes about thirty times as long as Earth does to complete one orbit. So as our planet whirls around the sun on an inside track, it catches up to Saturn and passes it nearly every year. This year Earth passed Saturn in mid-May. From our vantagepoint as riders on the Earth, as we caught up to Saturn and passed it, we saw the planet appear to stop moving in its usual easterly direction against the background stars -- and begin retrograde motion, or motion toward the west among the stars. It's as though we're riding in a fast car, passing a slower car, having that sense that the slower car is actually moving backwards against the distant landscape. In the same way, when Earth passes an outer planet, the planet appears to move backwards against the distant stars. Saturn has been retrograding now since March. Today it stops that backwards motion -- and is temporarily stationary, or poised against the background stars -- before it begins moving eastward again. If you watch Saturn carefully for the next several months -- and compare its position to that of the background stars -- you'll see that the planet really is moving in an easterly direction against the stars -- and perhaps get a sense of your own planet's movement through space. Script by Diana Hadley and Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin