Evening planets. Astronomical almanacs list the planet Saturn as stationary on July 21, 2014 at 15 UTC. That is 10 a.m. on July 21 for us in central North America. Convert to your time zone.
What does it mean? It doesn’t mean that Saturn – like Polaris, the North Star – will remain in the same place in the sky all through the night tonight. For all skywatchers, on all parts of Earth, Saturn will appear at its highest in the sky around sunset. It’ll descend westward, to set in the west shortly after midnight (1 a.m. local daylight-saving time). This movement of Saturn across the sky throughout the night is due to Earth’s spin.
Meanwhile, relative to the background stars, Saturn stays in one spot relative to the stars. That’s the meaning of stationary. Saturn is poised in front of the constellation Libra, momentarily motionless relative to Libra’s alpha 3rd-magnitude star Zubenelgenubi. Since March 3, 2014, Saturn has been moving in retrograde (westward) in the constellation Libra, heading toward the Libra star Zubenelgenubi. After today, Saturn will reverse course and begin moving prograde (eastward) in front of the stars. This movement of Saturn, first to the west and also to the east, is also due to Earth, in this case to our faster motion than Saturn in orbit.
Saturn is the most distant world you can easily see with the unaided eye. As a result, it moves rather slowly through the constellations of the Zodiac. Yet Saturn, the sixth planet outward from the sun, will finally leave Libra to enter the constellation Ophiuchus in January 2015.
Meanwhile, Saturn will appear stationary near the Libra star Zubenelgenubi for another week or so. Keep an eye on Saturn and Zubenelgenubi for the next several weeks in binoculars. How long will it take for you to discern Saturn’s motion relative to the brighter stars in the constellation Libra?
On the night of July 21, for instance, Saturn shines in front of Libra, near Libra’s alpha star Zubenelgenubi.
The red planet Mars and Spica, Virgo’s brightest star, will appear to the west of Saturn (toward the direction of your sunset). If you have binoculars, you can see that Zubenelgenubi, which appears single to the unaided eye, is actually a double star!
The ruddy star Antares will shine to the east of Saturn (outside this sky chart, toward the direction of your sunrise).
Before dawn, you’ll find the waning crescent moon in the east. The moon will pair up with the star Aldebaran in the morning hours on Tuesday, July 22. This star represents the fiery red eye of the Bull in the constellation Taurus. Will you be able to see Aldebaran’s red color in the moon’s glare? Maybe not on Tuesday morning, but Aldebaran will be there when the moon moves away.
Then keep on watching for the next several mornings, as the shrinking waning crescent approaches the planets Venus and Mercury in the morning sky. You can’t miss Venus. It’s the brightest thing up before dawn, besides the moon. Mercury is near Venus, closer to the horizon.
Bottom line: The golden planet Saturn is stationary – unmoving with respect to the stars – on the night of July 21, 2014. On the morning of July 22, watch for the red star Aldebaran near the moon before dawn. Notice the planets Venus and Mercury nearby. The moon will pass Venus and Mercury in the coming mornings.