- Planétarium Rio Tinto Alcan
From August 9 to 23, 2021
Mercury passed behind the Sun (superior conjunction) on August 1. The tiny planet reappears gradually in the evening sky where it undergoes a very poor apparition from about August 20 to September 15: using binoculars, look for Mercury very low in the west, 20 minutes after sunset. On the evening of August 18, Mercury (mag. –0.5) passes less than 9 arc minutes from much fainter Mars (mag. +1,8), but this conjunction will be very difficult to see as it happens very close to the western horizon, just 30 minutes after sunset.
Venus is the bright Evening Star that shines low in the west, 20 minutes after sunset; Venus itself sets less than 90 minutes after the Sun. On the evening of August 10, the thin crescent moon hangs 6 degrees to the right of Venus. The following evening, August 11, the lunar crescent shines 7 degrees to the upper left of the Evening Star.
Mars is becoming harder to see at dusk as the Sun catches up to it. About 30 minutes after sunset, scan the western horizon with binoculars in search of the Red Planet, to the lower right of bright Venus; Mars sets less than 45 minutes after the Sun. On the evening of August 9, the thin crescent moon shines 4 degrees to the upper right of Mars. On the evening of August 18, Mercury (mag. –0.5) passes less than 9 arc minutes from Mars (mag. +1,8), but this conjunction will be very difficult to see as it happens very close to the western horizon, just 30 minutes after sunset. The Red planet continues to sink in the glare of the setting Sun, and we lose sight of it completely after the third week of August.
Jupiter reaches opposition during the evening of August 19 and is visible all night long. The very bright Giant Planet appears in the east-southeast at dusk. Around 1 a.m., it shines brightly about 32 degrees high in the south, and then vanishes in the west-southwest at dawn. During the night of August 21 to 22, the full Moon passes less than 5 degrees below Jupiter.
Saturn was at opposition during the night of August 1 to 2, and presently visible nearly all night long. The Ringed Planet appears at dusk above the east-southeast horizon, culminates around midnight, 26 degrees high in the south and about 20 degrees to the right of very bright Jupiter, and sets at dawn in the west-southwest. During the night of August 20 to 21, the waxing gibbous Moon shines less than 5 degrees below Saturn.