Mars is the only bright planet to light up the evening sky throughout April 2021 (Jupiter and Saturn are found in the predawn/dawn sky all month long, while Venus sits too close to the sunset glare to be easily seen). Best to seek out this modestly-bright world at early evening, when it’s still relatively high in the sky. Mars slowly descends westward during the evening hours, finally setting in the west at or around midnight at mid-northern latitudes, and by mid-evening at temperate latitudes in the Southern Hemisphere.
Mars starts the month in front of the constellation Taurus the Bull and then passes into the constellation Gemini the Twins on April 24, 2021. Enjoy Mars in April 2021! It’s only going to get fainter as this year progresses. In the months ahead, Mars will slowly but surely dim as – day by day – it will sink closer and closer to the setting sun.
Let the moon help guide your eye to the red planet for several nights centered around April 16 or 17. If you live in Southeast Asia, you can witness the moon occulting – covering over – Mars on the night of April 17, 2021. Read more.
Venus will be hard to spot in April, because it’ll remain close to the sunset glare all month long, and will follow the sun beneath the horizon before dark. By late April – or more likely – May, Venus will return to our skies as an evening “star” near the western horizon. It’ll then be up in the evening, glorious, for the rest of this year.
For the utmost sky watching challenge, try catching the pairing of Mercury and Venus after sunset in the last week in April. Don’t forget binoculars!
Jupiter and Saturn remain somewhat close together, yet are slowly spreading apart, in the April predawn/dawn sky. Both planets are up before dawn’s first light, and will be much easier to view than they were last month.
Saturn rises first. At mid-northern latitudes, Saturn rises about 2 1/2 hours before the sun in early April, and about 3 1/2 hours before the sun at the month’s end. Jupiter follows Saturn into the sky about 1/2 hour later.
At temperate latitudes in the Southern Hemisphere, Saturn rises about 1 1/2 hours after midnight in early April, and by the month’s end, comes up around midnight. (By midnight, we mean midway between sunset and sunrise.) Jupiter follows Saturn into the sky roughly an hour later.
Use the moon to help guide you to the morning planets on April 5-8, 2021.
Mercury is not easy to see this month, as it transitions from the morning to evening sky. Mercury swings to superior conjunction (see diagram below) on April 19, 2021, to enter the evening sky. After that, Mercury will climb away from the sunset, to reach its greatest eastern (evening) elongation from the setting sun on May 17, 2021. From northerly latitudes, Mercury might first become visible after sunset by late April.
For the Northern Hemisphere, May 2021 will present the best month of the year to view Mercury in the evening sky.
What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually 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: April 2021 presents three bright planets! Mars is the only bright planet to light up the evening sky. Jupiter and Saturn appear in the morning sky. Venus is hard to see because she sits low at dusk, and follows the sun beneath the horizon before darkness falls. Mercury is difficult to view as well, because the solar system’s innermost planet transitions from the morning to evening sky in April 2021.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.