Santa's sleigh isn't even packed yet, but the December sky already has a few celestial gifts at the ready to close out 2018. So warm up your gloves by the fire, pour the hot chocolate and bundle up for a month of spectacular meteor showers, stargazing and a close pass from a green-glowing comet.
While the (new) moon is away, the stars will play (Dec. 7)
The Milky Way stretching over Lütispitz mountain in Switzerland. (Photo: Lukas Schlagenhauf/Flickr)
A new moon is when the moon is located on the same side of the Earth as the sun, and Dec. 7 will offer optimal conditions to head outside into the darkness and revel in Mother Nature's nighttime decorations. It's also the perfect time for hobbyist and professional astronomers alike to set up telescopes and check out galaxies, planets, asteroids or other distant objects.
Gaze upon the mysterious Geminids meteor shower (Dec. 13-14)
A colorful Geminid meteor captured over the volcano Mount Teide in the Canary Islands, Spain. (Photo: StarryEarth/Flickr)
One of the most prolific meteor showers of the year, with 120 to 160 shooting stars per hour, the Geminids are also one of the most scientifically perplexing. Whereas most meteor showers come from periodic comets shedding debris as they pass around the sun, the Geminids instead apparently are tied to an asteroid named 3200 Phaethon.
"Of all the debris streams Earth passes through every year, the Geminids' is by far the most massive," NASA astronomer Bill Cooke said in a statement. "When we add up the amount of dust in the Geminid stream, it outweighs other streams by factors of 5 to 500."
The problem is that the asteroid Phaethon (more on that below) is simply not large enough to account for this massive collection of debris. In fact, even though it ejects some dust as it heats during its rendezvous with the sun, the expelled mass accounts for only 0.01 percent of the total Geminids debris stream. The only other explanation scientists can come up with is that Phaethon was once much larger and much more chaotic with the amount of debris it spewed into space.
"We just don't know," Cooke said. "Every new thing we learn about the Geminids seems to deepen the mystery."
To gaze upon this mystery for yourself, look up on the evening of Dec. 13. The shower itself will peak on Dec. 14 at about 2 a.m. EST.
A hyperactive comet gives Earth a close shave (Dec. 16)
Comet Lovejoy glowing green above the Chilean Atacama Desert in 2015. Comet 46P Wirtanen may put on a similar green light show this December. (Photo: Shawn Stephens/Flickr)
On Dec. 16, after making a pass around the sun four days earlier, Comet 46/P Wirtanen will fly by Earth at a distance of only 7.2 million miles. According to astronomers, that makes it the 10th closest comet to graze Earth since 1950. As we detailed earlier this month, it could also turn out to be one of the brightest.
Despite its small size (less than a mile wide), Wirtanen has been known to release a greater amount of volatiles than other comets of similar scale. This phenomenon, termed a "hyperactive comet," can sometimes cause these relatively small rocks of frozen ice, rock, and dust to briefly become the largest objects in the Solar System as they near the sun. Were Wirtanen to experience such an outburst during its return trip back through the Solar System, it would offer a spectacle in the night sky unlike any we've seen in quite some time.
Even if this holiday comet fails to exceptionally brighten, it's still expected to be something a good pair of binoculars –– and maybe even the naked eye –– will be able to spot throughout late December.
During its closest approach to Earth in mid-December, seek out dark skies and look for it in the constellation Taurus. According to the One Minute Astronomer, locating this region among the heavens in thankfully relatively straight-forward.
If you can find Orion, finding Taurus is easy. Just extend the line of Orion's belt to the northwest until you find a bright orange star nestled in a V-shaped cluster of stars.
Celebrate the winter solstice (Dec. 21)
A hiker in Iceland observing the winter solstice in December 2014. (Photo: Hafsteinn Robertsson/Flickr)
The winter solstice, that brief moment when the sun is exactly over the Tropic of Capricorn, will take place on Dec. 21 at 5:23 p.m. EST.
While the winter solstice features the longest night of the year for those of us freezing in the Northern Hemisphere, it also brings with it the hope of more light in the days and months that follow. Because the sun is at its lowest arc in the sky, the 21st is also a time to get out and see extremely long shadows. "Your noontime shadow on the solstice is the longest it will be all year," MNN's Melissa Breyer points out. "Relish those long legs while you can."
Bask in the glow of the full Cold Moon (Dec. 22)
A 2016 November supermoon rising above Lick Observatory in California. (Photo: Wilson Lam/Flickr)
"The moon on the breast of the new-fallen snow, Gave a lustre of midday to objects below,
When what to my wondering eyes did appear, But a miniature sleigh and eight tiny rein-deer."
-- 'Twas the Night Before Christmas, Clement Clarke Moore
2018's last full moon will reach its peak at approximately 12:48 p.m. on Dec 22. The full moon will also be the longest one of the year and will appear for about three days surrounding it's peak time. By the time Dec. 25 rolls around, there should still be plenty of moonlight for Santa and his team of reindeer to navigate by.
While the Old Farmer's Almanac referred to December's big lunar event as the "Cold Full Moon," native people of North America also referred to it as the "Big Spirit Moon," "Blue Moon," and the "Snow Moon." In New Zealand, where summer will soon be underway, this lunar season is described as "birds are now sitting in their nests."
Catch the Ursids meteor shower (Dec. 23-24)
While the Ursids have a tough act to follow after the spectacular Geminids, this annual meteor shower is still capable of throwing down up to 10 shooting stars per hour. Originating from debris shed by Comet 8P/Tuttle, the Ursids appear to stream from the constellation Ursa Minor. Bundle up, get comfortable, and gaze up on the evening of the 23rd or 24th to catch the peak of this holiday shower.
Editor's note: This story has been updated since it was first published in December 2017.