March guide to the bright planets

Skywatcher, by Predrag Agatonovic.

Posted by Bruce McClure and Deborah Byrd

Mars is the only bright planet to light up the evening sky in March 2021. Mercury, Jupiter and Saturn are found in the predawn/dawn sky all month long, and Venus is lost in the sun’s glare.

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 resides in front of the constellation Taurus the Bull from now until well into April.

Enjoy Mars in March!

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.

The big event of the month comes in early March, as Mars and the Pleiades star cluster showcase their close conjunction on March 3. This will be their closest pairing on the sky’s dome since January

20, 1991. A closer Mars-Pleiades conjunction won’t happen again until February 4, 2038.

Let the moon help guide your eye to the red planet for several nights centered on or near March 19.

Venus – the brightest planet – reached its greatest elongation of 46 degrees from the sun in the morning sky last year on August 12 or 13, 2020, depending upon your time zone.

As March 2021 opens, however, Venus sits too close to the rising sun to be visible; and as March draws to a close, Venus looms too close to the setting sun to be seen.

Inferior conjunction – when Venus sweeps between the sun and Earth – happened on June 3, 2020. Some 10 weeks later, Venus reached its greatest elongation, or distance from the sun, in the morning sky on August 13, 2020. Its disk was about 50% illuminated by sunshine. In March 2021, Venus will start the month in the morning sky and end the month in the evening sky. On March 26, 2021, Venus will be at superior conjunction, to exit the morning sky and to enter the evening sky. Image via UCLA.

In other words, Venus – in its smaller, faster orbit around the sun – is about to “turn the corner” ahead of us in orbit. On March 26, Venus is to pass on the far side of the sun, to exit the morning sky and to enter the evening sky. That’s when this inferior planet will reach superior conjunction.

By late April or 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.

Jupiter and Saturn remain fairly close together in the eastern predawn/dawn sky throughout March 2021. Saturn rises first and Jupiter follows Saturn into the sky shortly thereafter. From northerly latitudes, Jupiter and Saturn might still be hard to view in the early part of the month. But they’re there, and, day by day, the planetary twosome will rise sooner before sunrise and appear a bit higher in the predawn/dawn sky. For the best view, find an unobstructed horizon in the direction of sunrise. Seek them out with binoculars first. Toward the end of the month, try seeing them with the eye alone.

Mercury, the innermost planet, bunches up with Jupiter and Saturn in the morning sky during the first week of March. Mercury actually has a conjunction with Jupiter on March 5, but his conjunction will probably be difficult to view from northerly latitudes.

Use the moon to help guide you to the morning planets on March 8, 9 and 10.

Mercury is a morning object all through March. Luckily for the Southern Hemisphere, March presents Mercury’s best apparition in the morning sky for the year. Given an unobstructed horizon and clear sky, you should have little trouble catching the Mercury-Jupiter conjunction on March 5, and the slender waning crescent moon sweeping by the three morning planets (Mercury, Jupiter and Saturn) on March 8, 9, 10 and 11.

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.

The red planet Mars has a conjunction with the Pleiades star cluster every other year. But the Mars-Pleiades conjunction on March 3, is the closest one since 1991. A closer Mars-Pleiades conjunction won’t occur again until 2038.
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