Venus is the brightest planet, beaming mightily in the east before sunrise. As December 2018 begins, Venus is shining at greatest brilliancy, its brightest for this morning apparition. Although Venus will remain a fixture of the morning sky until mid-August 2019, it’ll grow dimmer, by a bit, after early December. Even so, as always, Venus will rank as the third-brightest celestial body, after the sun and moon!
The waning crescent moon will join Venus in the morning sky for several days, centered on or near December 3. If you’re up before dawn, you can also see the stars Arcturus and Spica accompanying the moon and the queen planet, as depicted on the sky chart above.
At mid-northern latitudes, Venus rises about 3 1/2 hours before sunrise throughout December.
At temperate latitudes in the Southern Hemisphere, Venus rises about two hours before sunup in early December. By the month’s end, that’ll increase to about three hours.
Jupiter is the second-brightest planet, after Venus. This planet exited the evening sky, and entered the morning sky, in late November. In the first week or two of December, Jupiter rises only a little while before the sun. It’ll be hard to see in the glare of morning twilight.
Jupiter will become easier to see before sunrise around mid-December, when it rises an hour or so before the sun. Around this time, Mercury reaches its greatest western (morning) elongation of 21 degrees from the rising sun. Because Mercury will rise before Jupiter does in mid-December, an imaginary line from Venus through Mercury may enable you to locate Jupiter near the horizon. See the above sky chart.
After mid-December, Jupiter will climb upward toward Mercury, as Mercury is sinking downward, toward Jupiter. Circle December 21 on your calendar, and watch for these two worlds to meet up for a close-knit conjunction. See the sky chart below.
Jupiter rapidly climbs out of the glare of sunrise, coming up a solid two hours before the sun by the month’s end from most places worldwide. Mercury, though sinking sunward, will still rise a good hour before the sun on the last day of 2018. So, as the year draws to a close, watch for a picturesque line-up of the waning crescent moon with Venus, Jupiter and Mercury about an hour before sunrise on December 31, as shown on the sky chart below.
Mars and Saturn are the only two bright planets to appear in the December 2018 evening sky – though Saturn, for the most part, only nominally so. Saturn sinks closer and closer to the sunset throughout December, and by mid-December will set too soon after the sun to be visible. Your best chance of spotting Saturn may be at dusk/nightfall on December 8 and 9, when the young waxing crescent moon swings rather close to Saturn on the sky’s dome. See the sky chart below.
Fortunately, Mars remains bright and beautiful, shining more brilliantly than a 1st-magnitude star throughout December 2018. In December, Mars transits – reaches its highest point in the sky – at dusk in the Northern Hemisphere, yet before sunset in the Southern Hemisphere. Best of all, Mars stays out till around midnight in both the Northern and Southern Hemispheres.
Click here for recommended sky almanacs providing you with the transit times for Mars.
Watch for the moon to be in the vicinity of Mars for several evenings, centered on or near December 14. Fortunately, the moon will set before the peak hours of the Geminid meteor shower, centered around 2:00 a.m. wherever you are on the globe on December 13 and 14. See the sky chart below.
Saturn will swing over to the morning sky in January 2019, leaving Mars as the only bright planet to adorn the January 2019 evening sky.
Mercury, the innermost planet of the solar system, is a morning planet all month long in December 2018. Mercury might become visible before sunrise by the end of the first week of December. Look for Mercury beneath Venus, as shown on the sky chart below. By mid-December, Mercury rises about 90 minutes before the sun at mid-northern latitudes; from temperate latitudes in the Southern Hemisphere, it’s more like 75 minutes before sunrise. The crowning moment will come on the solstice, when Mercury and Jupiter have their conjunction on December 21.
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 2018, Mars shines in the evening sky all month long. Saturn disappears in the sunset glare by about mid-month. Venus lights up the eastern sky before sunrise all month. Mercury and Jupiter join Venus in the morning sky around mid-December. Click here for recommended almanacs; they can help you know when the planets rise, transit and set in your sky.
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.