The coming month brings back-to-back meteor showers, the moon posing with planets, and plenty more reasons to look up at the night sky. You’ll even have the chance to catch the only visible supermoon of 2017.
So dust off those binoculars and mark your December calendar!
Super Cold Moon and Aldebaran—December 3 and 4
The December full moon is often called the cold moon in the Northern Hemisphere, because of its coincidence with chilly temperatures. This year’s cold moon officially arrives at 10:47 a.m. ET (15:47 UTC) on the 3rd. Less than a day later, the lunar orb will make its closest approach to Earth, reaching a distance of only 222,443 miles.
The mashup of a full moon and the lunar orb’s close approach is popularly dubbed a supermoon, and December’s event will be the first and last you can see in 2017. On the night of December 3, the moon will appear about seven percent larger and 16 percent brighter than usual. (See our special viewer’s guide to December’s super cold moon.)
Also on December 3, try using binoculars or telescopes to spot the bright orange star Aldebaran near the moon. For lucky sky-watchers across northwestern North America, the moon will briefly eclipse this red giant star, part of the constellation Taurus, the bull, in the predawn sky. Viewers in northern Greenland and much of Asia will see the star slip behind the moon in the evening. You can use this table to find the exact times the star will wink out around the world.
Moon and Beehive—December 7
As a great observing challenge, look for the waning gibbous moon to point the way to the famous Beehive open star cluster in the constellation Cancer, the crab. This beautiful group of stars lies about 600 light-years from Earth and was mentioned as far back as 260 B.C. by Greek poet Aratos, who referred to it as “the little mist.” The cluster is visible with naked eyes as a faint and fuzzy patch in dark, clear skies. Suburban sky-watchers can also hunt it down easily using either binoculars or small telescopes.
Geminid Meteor Shower—December 13
The annual Geminid shower will reach its peak this night and into the following morning for viewers in the Americas. The Geminids are known to be quite prolific, with rates as high as 60 to 120 shooting stars an hour.
Views of the meteor shower are expected to be good on the nights before and after the peak as well. Sky-watchers will only have to contend with glare from the waning crescent moon, which sets early in the evening. Stay tuned for our detailed viewer’s guide on how to get the best out of this unique sky show.
Moon and Jupiter—December 14
Early risers on the 14th should see the waning crescent moon pose with the brilliant planet Jupiter. While they will seem close in the sky, the moon will be a mere 246,684 miles away, while Jupiter sits at a stately distance of 573 million miles from Earth. Adding to the celestial beauty, Mars will be to the upper right of the cosmic pair, while the bright star Spica will form a line with the two planets.
December Solstice—December 21
At 11:28 a.m. ET (16:28 UTC) on the 21st, the sun will be at its lowest point in the sky, making it the shortest day of the year north of the Equator. In the Southern Hemisphere, the sun will be at its highest point, making December 21 the longest day of the year. Seasons (and solstices) happen because Earth is tilted on its axis at it orbits the sun. During winter, the axis is slightly tilted away from the sun, so the hemisphere in question receives less sunlight. The exact date and time of the December solstice changes slightly from year to year because of the difference between a calendar year of 365 days and the solar year of 365.26 days—the exact time it takes for Earth to make one trip around the sun.
Ursid Meteor Shower—December 22
In the predawn hours of December 22, North Americans will see the peak of an annual meteor known as the Ursa Minorids, or the Ursids. This relatively minor shower will seem to radiate from their namesake constellation Ursa Minor, the little bear. Meteors will appear to shoot out from just above the bowl of the Little Dipper, the well-known star pattern, or asterism, that’s part of Ursa Minor.
While the Ursids only produce an average of 10 to 15 shooting stars an hour, on rare occasions viewers will catch bursts of 30 or more an hour. This year, the waxing crescent moon will set in the evening, so meteor watchers staying up late can expect to have the best dark skies possible.
Moon Meets Aldebaran, Act II—December 30
Sky-watchers around the world will get a second chance this month to catch a cosmic meeting between our moon and the red eye of Taurus. The brilliant duo will rise soon after darkness falls in the eastern sky. Try using binoculars to catch the orange hue of Aldebaran in the bright glare of the waxing gibbous moon.
Lucky onlookers in most of North America, Europe, and Western Russia will also see the star briefly vanish as it glides behind the moon beginning at around 8 p.m. ET (1:00 UTC on December 31).