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Venus – the brightest planet – has been in our evening sky for many weeks, but, especially from the Northern Hemisphere, has assumed a low profile, lurking low in the west after sunset. It’s in December 2019 that Venus will truly reclaim her identity as the dazzling evening “star.” Venus will become more noticeable to people around the world this month, ascending higher in the west after sunset each evening.
Venus regained some prominence last month, meeting with Jupiter – the second-brightest planet – in a stunning conjunction on November 24, 2019. Then the moon swept past these planets as November ended. As December begins, though, Jupiter is sinking into the sunset, following the sun beneath the horizon before nightfall.
And so – in the evening – you might turn your gaze not only toward Venus, but also toward Saturn, which was a bit-player during last month’s Venus-Jupiter drama. Now, though – even as Saturn edges closer to the sunset glare – Venus is edging upward, away from the sunset. Venus will catch up with Saturn on December 10, 2019, and the two planets will meet for a conjunction. Saturn nowhere matches Venus in brilliance. In fact, Venus outshines Saturn by more than 60 times. But Saturn does shine on par with the 1st-magnitude stars, the sky’s brightest stars.
Meanwhile, in the morning sky in early December, watch for both Mercury and Mars. Mercury, the solar system’s innermost planet, reached its greatest elongation from the sun in the morning sky on November 28, 2019. It remains a fine morning object as viewed from the Northern Hemisphere for the first week or two in December. Get up before dawn to see the 1st-magnitude star Spica lining up with the 2nd-magnitude planet Mars. Then, as the predawn darkness gives way to dawn, look for Mercury to climb above the horizon, more or less on a line with Spica and Mars.
After Mercury disappears back into the dawn – after the first week or 10 days of December – people around the world will still see modestly-bright Mars, rising before dawn’s first light in the morning sky. At mid-northern latitudes, Mars rises about 2 1/2 hours before the sun in early December, and by the month’s end, rises some 3 hours before.
At temperate latitudes in the Southern Hemisphere, Mars comes up about 1 1/2 hours before the sun in early December, and about 2 1/2 hours before sunrise at the month’s end.
Mars is now in that part of its cycle with respect to Earth in which it’ll hover – faint and not at all noticeable – in our predawn sky for some months. Mars was in conjunction with the sun, or most behinds the sun as seen from Earth – on September 2, 2019. And now it remains far across the solar system from us, with Earth speeding around in its orbit, trying to catch Mars again. But it’ll be some months before we catch it.
And thus Mars alternates years in being bright in our sky, or faint. 2019 was a dull year, but 2020 will be an exciting one, for Mars! It’ll start slowly, though, with Mars sitting low in the east (much as it is now) as the year begins. January, February, March, April 2020 … you’ll still find Mars doing nothing much, low in the east before sunup. Earth will still be far across the solar system from Mars, but rushing along in our smaller, faster orbit, trying to catch up. As northern summer 2020 approaches, Mars will begin to change. It’ll begin to brighten more dramatically as, finally, Earth begins to catch up to Mars. The Red Planet will appear brightest in our sky – very bright indeed and fiery red – around the time of its opposition on October 13, 2020.
Let the old moon help guide your eye to Mars for several mornings, centered on or near December 22, as shown on the sky chart below.
And what of the evening planets? What is their fate? By the second half of December, Jupiter and Saturn will both fade away in the evening twilight. As seen from above the solar system, Earth will be fleeing far ahead of them in our smaller, faster orbit, placing the sun between us and them. Jupiter will surely be gone by mid-December (and likely before that); it’ll swing behind the sun, reaching its yearly conjunction with the sun, on December 27. Afterwards, Jupiter will come back to the morning sky in January, 2020.
Saturn will last a bit longer in our sky in December 2019, sitting low in the glow of evening twilight, difficult to see. Saturn will swing directly behind the sun on January 13, 2020, to transition out of the evening sky and into the morning sky. After December passes, you might not see Saturn again until the ringed planet reappears in the eastern morning sky in February 2020.
Meanwhile, dazzling Venus will grace the evening sky for the first part of 2020. And, as if to remind us of her prominence, Venus will meet again with the moon as the year ends.
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: In December 2019, a lineup of three planets – Jupiter, Venus, Saturn – can be found in the west after sunset. Venus is brightest, and starts out in the middle of this line. Day by day, Venus will climb upward toward Saturn, until Venus and Saturn meet up for a conjunction on December 10. As the month begins, both Mercury and Mars rise in the east before the sun at each morning’s dawn. Mercury will drop into the sun’s glare, but Mars will remain in the eastern predawn sky, slowly but surely brightening.
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.