Three bright planets – Jupiter, Venus, Saturn – can still be found in the west after sunset. Day by day, Venus will climb upward while Jupiter and Saturn sink toward the sunset glare. Venus and Saturn will meet up for a conjunction on December 10. In the morning sky, as the month begins, keep watching for Mercury and Mars. They rise in the east before the sun.
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 this month 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. 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, 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 first-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.
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 first-magnitude star Spica lining up with the second-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, 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 three 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.
Let the old moon help guide your eye to Mars for several mornings, centered on or near December 22.
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.
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.