Although Saturn shines as brilliantly as a first-magnitude star, Venus outshines Saturn by about 80 times. If you can’t see Saturn on these September evenings, try aiming binoculars at Venus to spot Saturn nearby. Venus and Saturn will occupy the same binocular field of view from about September 15 to September 21.
Be sure to catch these two worlds as they come out at dusk and nightfall. As the Earth rotates eastward on its axis, Venus and Saturn (and the faint star Zubenelgenubi to the east of these planets) will sink westward, to set at early evening at mid-northern latitudes. At more southerly latitudes, these two planets and the star Zubenelgenubi stay out later after dark. At our northerly latitudes, we may need binoculars to see Zubenelgenubi.
The planets Venus and Saturn are going eastward through the constellations of the Zodiac, heading for Zubenelgenubi, the alpha star of the constellation Libra the Scales. Venus, the second planet outward from the sun, circles the sun much more quickly than does Saturn, the sixth planet outward.
For the rest of this month, watch Venus and Saturn race eastward along the ecliptic – the pathway of the planets in front of the backdrop stars. Venus will catch up with the star Zubenelgenubi on September 24, 2013, but Saturn won’t reach this milestone until mid-November 2013. By that time, Saturn and Zubenelgenubi will have shifted into the eastern morning sky, to sit deep in the glow of dawn and probably not visible to the unaided eye.
Swift-moving Venus will remain a fixture of the evening sky for the rest of this year. So watch for Venus to race by Saturn in the western evening sky over the next few days, starting today!