dipper@utastro.UUCP (Debbie Byrd) (06/23/85)
The giant world Neptune is at opposition today. More about it -- when we come back. June 23 Neptune at Opposition Sunday afternoon the Earth gains a lap on the planet Neptune -- as it does nearly every year -- since our world has a smaller circuit to make around the sun -- and since we move at about 18 miles per second, compared to only about three miles per second for Neptune. For a brief time on Sunday afternoon, Earth and Neptune are moving neck-and-neck in orbit. Then the moment is past -- and Earth pulls ahead of this giant outer world. Today, then, is Neptune's day of opposition to the sun. In Sunday night's sky, Neptune rises when the sun sets -- and wheels across the sky until the sun rises again at dawn. People on Earth with binoculars or small telescopes can locate Neptune now in the constellation Sagittarius. It's in a star-rich region of the Milky Way -- visible as a tiny greenish or bluish disk -- remote -- and completely featureless. Neptune now holds the distinction of being the outermost world in the solar system. That's been the case since January of 1979, when the tiny world Pluto inched close enough to the sun to be inside Neptune's orbit. This arrangement stems from the elongated orbit of Pluto -- and it's only temporary. By the end of the century, Pluto will once again be beyond Neptune -- where it'll stay for the next two hundred years. We don't know much about Neptune, because it's so faint and faraway. It's a gaseous planet -- four times larger than Earth -- but smaller than Jupiter or Saturn. The Voyager spacecraft may last long enough to visit Neptune -- in the year 1989. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin