Mercury is the smallest, and fastest, of the eight planets in our solar system: It takes 88 days to orbit the Sun, which means it switches from the eastern to western horizon, and visa versa, every month-and-a-half. As the month begins, Mercury rises low in the east about 50 minutes before the Sun. But you shouldn’t waste any time if you want to spot the fleeting planet since it disappears in the glow of daybreak within half-an-hour. Starting around 5:45 A.M., use binoculars to scan the eastern sky and you will find Mercury about half-a-field of view above the horizon.
On September 1, the tiny planet is located less than 1 ½ degrees to the left of Regulus, the brightest star in Leo; this conjunction will provide a good opportunity to confirm your observation. Mercury is currently closing in on the Sun at a rate of about 1 degree per day: By September 5th it will vanish in the glow of morning twilight and won’t reappear until mid-October. However, October’s apparition will not be favourable so this is your last chance to see Mercury for a while.
Venus, the Morning Star, begins the month in Gemini and is well above the eastern horizon during the pre-dawn hours; its incredible brilliance sets it apart from all other objects in the sky. By September 4, Venus moves into Cancer, en route toward a spectacular mid-month conjunction with M44, the famous Beehive star cluster at the heart of the Crab. Early risers can follow Venus with binoculars, as its orbital motion carries it eastward against the background stars. On the morning of September 12, the dazzling planet will be located just 2 ½ degrees to the right of the Beehive — well within a binocular field of view. Though this isn’t the closest conjunction of the month, it certainly promises to be the most dramatic, especially since a thin crescent Moon will be in the picture less than 5 degrees to the right of Venus. But wait! Venus isn’t done yet…
By September 23, the Morning Star moves from Cancer into Leo and heads toward a very close conjunction with the bright star, Regulus. On the 30th of the month, the two objects will be less than 3 ½ degrees apart, and the gap will continue to close until October 3 when they will be less than 1/10 of-a-degree apart! Stay tuned for more…
Jupiter and the Hyades
At the beginning of September, Jupiter rises in the east around 11:30 P.M., among the stars of Taurus, and remains visible throughout the second half of the night. However, as the evenings progress, the giant planet rises earlier and earlier until, by month’s end, it appears above the horizon at 9:30 P.M. You will find Jupiter located to the left of the Hyades star cluster — the nose of Taurus — which appears like a sideways “V” pointing to the right. Though the star cluster is visible to the unaided eye, binoculars reveal many more stars.
At 10:30 P.M., on the evening of September 7, the last quarter Moon will be located just 5 degrees to the right of Jupiter, and above Aldebaran. But keep watching! On the following morning, September 8, at 5:30 A.M., the Moon will have moved, on its orbit around the Earth, to a position scarcely 1 degree to Jupiter’s right! Yet another spectacular conjunction.
Mars and Saturn in the evening
Mars and Saturn begin the month in the constellation of Virgo. The two planets can be found low in the southwest around an hour after sunset; both are at the same altitude, and are about 10 degrees apart. Saturn is the slightly brighter object on the right and is located 5 degrees above Spica, the bright blue star in Virgo. However, this situation changes rapidly as Mars, the faster of the two, moves eastward, away from the ringed planet, and slightly higher in the sky: By month’s end, Mars will be well within Libra and more than 26 degrees to the upper left of Saturn. The two planets set progressively earlier each evening and Saturn will vanish in the glow of twilight during the last week of the month — but not before putting on one last show…
On the evening of September 18, about 45 minutes after sunset, scan the western horizon with binoculars and you’ll see a thin crescent Moon hovering midway between Mars and Saturn. And then, for the grand finale, the following evening of September 19, scan the sky for Mars about half-an-hour after sunset, and you’ll see a slightly thicker lunar crescent positioned just 1 ½ degrees to the left of the Red Planet.
There you have it, five splendid conjunctions this month… and another yet to come. With so many opportunities you’re bound to catch at least one or two. Good luck, and…
Clear skies!
