As the December holiday season gets into full swing, sky-watchers around the world will receive some early celestial presents, including plentiful comet sightings, five moon pairings, two meteor showers, and a stunning solstice night.
So dust off those binoculars, and get set to explore the night sky this month.
Catch some comets—early December
On November 7, three amateur astronomers separately discovered a quickly brightening comet, now called C/2018 V1 Machholz-Fujikawa-Iwamoto. The icy visitor is shedding gas and dust as it heads toward the sun from the Oort cloud, an enigmatic reservoir of icy debris at the edge of the solar system.
Current predictions have this comet continuing to brighten and possibly reaching magnitude 5 in the first week of December, which would make it an easy viewing target with binoculars. Chasing the comet may be a bit tricky, though, as it will set soon after the sun does in the western horizon.
Luckily, sky-watchers will get a rare chance this month to hunt down a second comet known as 46P/Wirtanen that may be easier to spot. This giant ball of ice and rock speeds through the inner solar system every six years, and it will make its closest approach to the sun on December 12. At that point, predictions say it may even become bright enough to barely see with the naked eye.
This comet will spend the first half of the month wading through the faint constellation Eridanus, the river, next door to much brighter Taurus, the bull, in the late-night sky. Catch your views of this frozen interloper soon, since it is expected to begin fading quickly by the second half of December.
Moon meets stellar pair—December 2-4
Early morning risers should watch the southeast sky for the bright duo of the planet Venus and the star Spica. The waning crescent moon will join the bright pairing to form an eye-catching celestial triangle in the first week of the month.
Saturn joins moon—December 8
As an observing challenge, look on this night for the waxing lunar crescent hanging very low in the western sky next to star-like Saturn. The cosmic pairing will be best seen at dusk, about 30 minutes after local sunset, through binoculars.
Geminid meteor shower peaks—December 13
Look toward the northeast from the late evening into the predawn hours for the annual Geminid meteor shower to kick into high gear. The best views will be from the dark countryside, far away from city lights.
Unlike other meteor showers, in which a comet is the source of the particles that streak through the atmosphere, the Geminids were born from a weird asteroid named Phaethon that appears to show cometary activity. Earth will slam into the thickest part of the asteroid’s debris field on the night of the 13th. And with the waxing crescent moon setting well before the shower peaks, expectations this year are for the Geminids to produce 30 to 60 shooting stars an hour at their peak.
Moon meets Mars—December 14
As evening twilight sets in, look for the moon in a beautiful pairing with ruddy Mars, with both celestial objects setting together in the west before local midnight.
Winter or summer solstice—December 21
At exactly 5:23 p.m. ET on the 21st, the sun will be at its lowest point in the sky for the year, making it the shortest day of 2018 for people north of the Equator and ushering in the winter solstice. The sun will be at its highest point for viewers in the south, marking the longest day of the year and the summer solstice for that half of the planet.
Earth is tilted on its axis relative to the sun, so that different halves of the planet receive more or less sunlight as the world moves in its orbit. When Earth’s Northern Hemisphere is slightly tilted away from the sun, people there experience winter, while people in the Southern Hemisphere are enjoying summer. The exact date and time of the December solstice changes slightly from year to year, but it usually falls around December 21.
Ursid meteor shower peaks—December 22
In your local predawn skies, look for a minor meteor shower known as the Ursids to peak on December 22. Earth will slam into the debris shed from the shower’s parent comet, 8P/Tuttle, between December 17 and 23. During this time, meteors will appear to shoot out from a region of sky just above the bowl of the Little Dipper asterism, which is part of the shower’s namesake constellation, Ursa Minor, the small bear.
While the Ursids produce about 10 to 15 shooting stars an hour, on average, at rare times during the peak they can deliver bursts of 30 or more meteors an hour.
Moon buzzes a beehive—December 24
On Christmas Eve, watch for the nearly full moon to be posing next to the Beehive open star cluster in the constellation Cancer, the crab. The cluster, which will be an easy target for viewers with binoculars, contains over a thousand stars that are grouped together about 577 light-years away.
Moon meets the maiden—December 30-31
At dawn on the last two days of 2018, look high in the southern sky for the beautiful waxing crescent moon to glide past the bright jewel-like star Spica. This stellar beacon shines with a distinct blue-white color. It is the brightest member of the stellar pattern that marks the constellation Virgo, the maiden, which is the largest constellation in the entire sky. (Can you recognize the constellations of the zodiac? Take our quiz to find out.)