EarthSky’s August 2021 guide to visible planets
Visible planets, the moon and more
Venus, Mars and Mercury
The bright planet Venus will remain a fixture of our evening sky for the rest of 2021. This is our sky’s brightest planet and it’s very easy to spot in the west after sunset. Two other planets – Mars and Mercury – will be up there as well, but – especially from the Northern Hemisphere – will take a deliberate effort to see. Mars will be easier to find in early August, and Mercury will be easier to find at the end of the month. Mars and Mercury sit beneath Venus, close to the western horizon at dusk. They set before darkness falls. Nominally, both Mars and Mercury reign as evening objects throughout August and September 2021. Realistically, though, these two worlds will be tough to catch in the afterglow of sunset from mid-and-far northern latitudes, even with binoculars.
The Southern Hemisphere has a big advantage in spotting Mars and Mercury. Your best bet is to spot dazzling Venus first, and then seek out these fainter planets below Venus.
Mars starts out the month quite high above Mercury, yet ends the month below Mercury. The two will stage 2021’s closest planetary conjunction on August 19, 2021. Will you see it? Bring along binoculars if you want to try!
Watch for the young lunar crescent to return to the evening sky on August 9 or 10. The moon and Venus will present a glorious picture in the evening twilight. From the Southern Hemisphere – on or near August 9 – you might even spot the whisker-thin crescent pairing up with much fainter Mars below Venus. Try your luck with binoculars.
Find out both the sunset time and the time of nightfall (end of astronomical twilight) via timeanddate.com.
Venus boldly shines in the evening sky for the rest of this year, to reach its greatest elongation from the sun on October 29, 2021 (see diagram below). Moreover, Venus will attain its greatest brilliance as the evening “star” at the time of the new moon on December 4, 2021.
Circle this date on your calendar, and see if it’s true that Venus can cast a shadow on a dark night!
Jupiter and Saturn
In August 2021, you can see the giant planet Jupiter and ringed planet Saturn from early evening until dawn. They’re at their most glorious this month. Both of them will have an opposition, when they will appear opposite the sun as seen from Earth, in August. Saturn will be at opposition on August 1-2. And Jupiter will be at opposition on August 19-20.
Opposition marks the middle of the best time of year to see a planet. Look for them in your southeast sky at nightfall/early evening, highest up around midnight, and low in the west near sunrise.
Do you have an unobstructed horizon from east to west? If so, look for Venus to blaze away in your western sky at dusk/nightfall. At the same time, you may also view Jupiter and Saturn low in the southeast sky. Some people might catch all three worlds in the same sky as early as August 1. From anywhere worldwide, though, it’ll be easier to see all three planets at dusk/nightfall as the month progresses.
Saturn rises first. Around the world, Saturn rises around sunset at the beginning of the month. At mid-northern latitudes, Jupiter follows Saturn into the sky about an hour (60 minutes) after Saturn comes up. At temperate latitudes in the Southern Hemisphere, Jupiter follows Saturn into the sky around 1 1/2 hours (90 minutes) after Saturn rises.
By around August 20, Jupiter will rise around sunset and set around sunrise. Saturn, which rises before Jupiter, will set about 1 1/2 hours (90 minutes) before Jupiter at mid-northern latitudes. At temperate latitudes in the Southern Hemisphere, Saturn will set about one hour (60 minutes) before Jupiter. Watch for Jupiter to follow Saturn across the nighttime sky throughout August 2021.
Which ones are the bright planets?
In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These are the planets easily visible without an optical aid. They’re the planets watched by our ancestors since time immemorial. These planets do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars.
You can spot them, and come to know them as faithful friends, if you try.
Bottom line: All you need to know about how to find the bright planets of the solar system during the month of August 2021.