December is certainly a great month for planet watchers. Venus finally becomes the preeminent evening star, by climbing well up into the southwest evening sky during this month.
The planet that ranks second in brightness to Venus is Jupiter and this month it arrives at opposition to the sun, rising at sunset in the east-northeast, then climbing high up into the southern sky during the middle of the night, and then descending the west-northwest sky at the break of dawn. Situated among the bright stars of Taurus the Bull, it adds additional luster to the glorious stars and constellations of the winter season.
Although not as dazzling as Venus and Jupiter, Saturn is well placed in the southern part of the sky at nightfall. It shines as bright as a first-magnitude star, but it appears even more bright because it is placed amidst the relatively faint star background of Aquarius the Water Carrier. Of course, if you have access to a telescope, by all means train them on Saturn in order to get a glimpse of its famous ring system.
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Looking for a telescope for the next night sky event? We recommend the Celestron StarSense Explorer DX 130AZ as the top pick for basic astrophotography in our best beginner's telescope guide.
Let's not forget Mars, which continues to noticeably brighten as it approaches the Earth. Each night during December, it draws 427,900 miles (688,500 km) closer to Earth and as a consequence this allows it to double in brightness as the month progresses. Even a casual observer who steps outside during late-evening hours cannot help but notice it in the east-northeast; it literally calls attention to itself, partly because of its luminosity, but also because of its distinctive fiery orange-yellow hue.
Finally, there is speedy little Mercury, normally difficult to see because of its close proximity to the sun, but during the latter half of December it should be easy to pick out, low in the east-southeast sky an hour or so before sunrise; its best morning apparition of 2024.
In our schedule, remember that when measuring the angular separation between two celestial objects, your clenched fist held at arm's length measures roughly 10 degrees. Here, we present a schedule below which provides some of the best planet viewing times as well directing you as to where to look to see them.
Be sure to check out our best telescopes for viewing planets guide and our more general guides for the best binoculars and the best telescopes. If you're interested in taking your own impressive skywatching images, we have recommendations for the best cameras for astrophotography and the best lenses for astrophotography.
The Sun
The sun reaches its southernmost point in the sky and begins its six-month return northward, repeating its annual promise (for those living north of the equator) of another spring and summer to come. The solstice occurs at 4:21 a.m. Eastern standard time. By convention this moment marks the change of seasons – the beginning of winter in the Northern Hemisphere and summer in the Southern.
Mercury
Mercury passes inferior conjunction with the sun on Dec. 5. And yet the planet makes an unusually sudden entry into our morning sky. By the 13th the +1.0-magnitude planet will be 15 degrees from the sun and will rise 1.3 hours ahead of it. On Dec. 23 Mercury will be 7 degrees to the upper left of Antares, and at magnitude -0.3 will be more than three times brighter than that reddish star.
By Christmas Eve (Dec. 24) Mercury will stand at greatest elongation, 22 degrees west of the sun. This is the best morning apparition of 2024. As seen from latitude 40 degrees north, Mercury will rise in the east-southeast before the start of astronomical twilight on Dec. 17 through Dec. 29.
On Dec. 28, a slender crescent moon will sit only about 1 degree to the right of Antares, with Mercury shining about 9 degrees to the left. This planet will remain a morning sky sight through the first week of January as it slowly moves toward superior conjunction.
Venus
On the evening of Dec. 4, Venus will sit about 3 degrees directly above a lovely waxing crescent moon. The dazzling evening star soars from excellent to magnificent prominence in the southwest at nightfall during the course of December. Viewers around latitude 40 degrees north see this resplendent planet’s sunset altitude increase from 21 degrees to 31 degrees during the month, and the interval by which it follows the sun grows from three to almost four hours.
The big reason for Venus's improved visibility to northerners is its northward movement along the zodiac at a time when the sun is reaching its most southerly point in Sagittarius at the December solstice.
Mars
Mars brightens during December from magnitude -0.5 to -1.2 as it nears opposition. It now outshines all starlike evening objects except Venus, Jupiter and Sirius. On Dec. 1, it rises in the east-northeast about 4 hours after sunset; by the 31st, only 80 minutes.
On Dec. 7 Mars becomes stationary 2 degrees north of the Beehive star cluster in Cancer, but retrograde motion will carry the planet 6.5 degrees northwest of that cluster on New Year's Eve. On Dec. 17, late evening skywatchers will take note of a waning gibbous moon that will be positioned less than 3degrees above this brilliant orange starlike planet.
Jupiter
Jupiter arrives at opposition to the sun on Dec. 7, and remains visible almost all night long during this month, reaching its highest in the south in the middle of the night and shining at its biggest and brightest, shining at magnitude -2.8. Jupiter still has the orange 1st-magnitude star Aldebaran and the two great star clusters of Taurus, the Hyades and Pleiades as sidekicks. On the evening of Dec. 14, take note that Jupiter sits almost exactly midway between the nearly full moon and Aldebaran.
Saturn
Saturn will be situated about 6 degrees to the upper left of a fat waxing crescent moon on Dec. 7. At nightfall this magnitude +1.0 planet is due south when December begins; a little west of south as the weeks go by.
Note Saturn's position against the stars and you’ll see it picking up speed as it moves eastward with respect to the dim stars of eastern Aquarius. During the month its brightness fades a trifle, and in a telescope its rings close a bit from 5 degrees to 4 degrees.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications.
Editor's Note: If you get a great photo of any of the planets and would like to share it with Space.com's readers, send your photo(s), comments, and your name and location to spacephotos@space.com.
