- Planétarium Rio Tinto Alcan
From August 13 to 27, 2018
In August, four planets are visible at twilight between the west and southeast. Appearing from right to left are Venus, Jupiter, Saturn and Mars. The Moon is also part of the scene from the 13th to 23rd; on August 14, the crescent Moon hangs a few degrees above Venus. Catch all five in a single viewing about 40 minutes after sunset in the colourful twilight sky; Venus is the first to sink below the horizon soon thereafter.
Mercury passed between Earth and the Sun (inferior conjunction) on August 8 and gradually reappears after August 20. Look for the tiny planet low in the east-northeast, 45 minutes before sunrise. Mercury becomes much brighter — and easier to see — in the last days of August and during the first week of September.
Venus is the bright Evening Star that pierces through the colours of twilight in the west-southwest, as soon as the sky begins to darken minutes after sunset. Venus is presently at greatest elongation from the Sun, but the inclination of its orbit keeps the planet close to the horizon during evening twilight: as a consequence, Venus now sets less than 1 ½ hours after our daytime star. At dusk on August 14, the lunar crescent hangs 6 degrees above Venus: with binoculars, admire the earthshine that dimly lights the otherwise dark section of the lunar disc. The scene becomes truly magnificent when the sky darkens, 30 to 45 minutes after sunset.
Mars was at opposition on July 27, and it’s presently closer to Earth, larger and brighter than at any time in the past 15 years; for a few more weeks, it even outshines bright Jupiter. Mars appears low in the southeast at dusk, culminates around 11 p.m. barely 18 degrees high in the south, and sets in the southwest around 3 a.m. Mars is presently performing its retrograde loop: until late August, it is moving westward (toward the right) with respect to the background stars. During the night of August 22 to 23 and 23 to 24, the waxing gibbous moon will shine near the Red Planet.
Jupiter appears above the southwest horizon during evening twilight and spends the rest of the evening slowly descending toward the west-southwest horizon where it vanishes before 11 p.m. The waxing Moon will appear near Jupiter on the evenings of August 16 and 17.
Saturn appears during evening twilight about 22 degrees high in the south, and then gradually descends toward the southwest horizon where it vanishes around 1 a.m. During the night of August 20 to 21, the waxing gibbous moon shines a few degrees to the right of the ringed planet.