Meteor Showers, a Supermoon, and the Solstice: A Guide to the December Night Sky

Thomas Coex/AFP/Getty Images
Thomas Coex/AFP/Getty Images

This has been a fantastic year for sky watching. Eclipses in particular had their day in the Sun, with celestial objects blotting each other out as if in competition. There was a penumbral lunar eclipse and an annular solar eclipse in February, and then in August, a partial lunar eclipse was followed up by a mind-blowing total solar eclipse. If you missed any or all of those events, don't lose heart: they will happen again and again and again, in your lifetime and beyond. Celestial mechanics guarantee it. The year isn't over yet, though, and December has a few wonderful events up its sleeve. Here are four things you should be on the lookout for in the skies above.

DECEMBER 3: THE ONLY SUPERMOON OF 2017

I know, supermoons are so 2016. There were six that year, if you don't recall. (I do, because I had to think of new things to write about every single one of them.) This year has been a bit less active in terms of super lunar events, with a total of zero must-see giant moons for your viewing pleasure. That changes on December 3 with the first and only supermoon of the year, and it has a great name at that: the Full Cold Supermoon. The "cold" part of the name, according to the Old Farmers Almanac, derives from Native American tradition. (They weren't being creative here; it's just really cold in December.) The "super" part is because the Moon will be at perigee—that is, the closest to Earth it's going to get in its orbit. The moon's orbit is not a perfect circle, meaning it sometimes appears larger in the sky than others.

Expect a moon that's about 14 percent larger than when it is at apogee (farthest from Earth), though, unless you are an obsessive moonwatcher, the larger size will be nearly imperceptible. My advice is to point at the moon when your friends are around and say something like, “Hey, check that out. I think that's a supermoon! You might not notice a difference, but I sure do. Compared to the moon at apogee, it's huge! Why, it's got to be 14 percent larger, at least. Wow!” Then change the subject quickly, because nobody likes a know-it-all.

DECEMBER 13–14: MORE THAN 100 METEORS PER HOUR

The Geminid meteor shower is considered the best meteor shower of the year, and it peaks after midnight between December 13 and 14. If you are in an area of low (or no) light pollution, and if you give your eyes an hour to adjust to total darkness, and if the weather is good (a lot of "ifs," but worth it if you can arrange things), you can expect to see more than 100 meteors per hour. Geminid meteors are a result of the Earth colliding into the debris field of the asteroid Phaethon, an unusual "rock comet" that leaves behind dust- and sand-sized particles as it circles the Sun. A speck of dust might not seem like much, but when the atmosphere of a 13,170,000,000,000,000,000,000,000-pound planet plows into it at tens of thousands of miles per hour, it is vaporized in a beautiful streak of light.

As if that isn't cool enough, on December 16, Phaethon itself will make its closest approach to Earth in 43 years! Yes, the Minor Planet Center officially considers Phaethon to be a "potentially hazardous object," but before you dust off your Y2K prepper supplies, know that the asteroid will be 27 times farther away than the Moon generally is from the Earth. Sadly, it is unlikely to affect the meteor shower in any measurable way.

DECEMBER 21: THE WINTER SOLSTICE

December 21 will play host to the longest night of the year. Why? Because the Earth's axis is tilted by about 23.5 degrees, and as we orbit the Sun, different latitudes are in direct sunlight. Presently, the southern hemisphere is “closer” to the Sun than the northern. On the 21st, the Tropic of Capricorn (latitude -23.5 degrees) will be in the overhead sun and will receive 13 hours, 27 minutes of daylight. The higher in latitude you go from the Tropic of Capricorn, the less daylight that part of the Earth will receive. The equator will get 12 hours of sunlight. The North Pole will get zero seconds of daylight. The Tropic of Cancer will get about 10.5 hours.

We call this the Winter Solstice, and it's when you'll find some of the best parties of the year. That much night, after all, and anything can happen. Starting on the 22nd, the days will begin to get longer in the northern hemisphere, with spring soon to follow.

DECEMBER 22: THE URSID METEOR SHOWER

Just before sunrise on the morning of December 22, as you're stumbling home from that killer Winter Solstice party, look up. Well, first find a spot with low light pollution and give your eyes time to adjust, and then look up. You will be treated to the annual Ursid meteor shower, here to ring out 2017—and not a minute too soon.

The Ursids are no Geminids; at best you'll only catch 10 meteors an hour, but because the Moon will be but a sliver, the natural skies should be nice and dark. Weather not cooperating? Don't worry. You should be able to catch an Ursid or two through December 25. (Note that on the night of the 24th, what you suspect is an Ursid might be a sleigh carrying cargo and an elderly, bearded man. A distinct red hue will help you distinguish the two. One is a shooting star. The other is Rudolph's nose.)

How to See the Full Sturgeon Moon on Thursday

Brook Mitchell, Stringer/Getty Images
Brook Mitchell, Stringer/Getty Images

The full moon of every month has a special nickname. Some—like September's harvest moon, December's cold moon, and May's flower moon—have obvious connections to their seasons, while other names are harder to decode. August's sturgeon moon is an example of the latter. It may not be the prettiest lunar title in The Old Farmer's Almanac, but that doesn't mean the event itself on August 15, 2019 won't be a spectacular sight to behold.

What is a Full Sturgeon Moon?

The first (and normally the only) full moon that occurs in August is called a sturgeon moon. The name may have originated with Native American tribes living around the Great Lakes in the Midwest and Lake Champlain in New England. These bodies of water contain lake sturgeon, a species of freshwater fish that grows up to 6.5 feet in length and can live 55 years or longer. August's full moon was dubbed the sturgeon moon to reflect its harvesting season. This full moon is sometimes called the green corn moon, the grain moon, and the blackberry moon for similar reasons.

When to See the Full Sturgeon Moon

On Thursday, August 15, the full sturgeon moon will be highly visible around sunrise and sunset. The satellite will be 99.9 percent illuminated by the sun when it sets Thursday morning at 5:57 a.m EDT—just nine minutes before dawn. On the West Coast, the setting moon will coincide perfectly with the rising sun at 6:15 a.m. PDT.

If you aren't interested in getting out of bed early to catch the sturgeon moon, wait until Thursday evening to look to the horizon. Twenty-seven minutes after sunset, the full moon will rise on the East Coast at 8:21 p.m. EDT. On the West Coast it rises at 8:10 p.m. PDT, 30 minutes after the sun sets.

The moon generally looks bigger and brighter when it's near the horizon, so twilight and dawn are ideal times to catch the spectacle. But it's worth taking another peek at the sky closer to midnight Thursday night; the Perseid meteor shower is currently active, and though the light of the moon may wash them out, you're most likely to spot a shooting star in the late night and early morning hours.

A Full Harvest Moon Is Coming in September

suerob/iStock via Getty Images
suerob/iStock via Getty Images

The Old Farmer's Almanac lists a special name for every month's full moon, from January's wolf moon to December's cold moon. Even if you're just a casual astronomy fan, you've likely heard the name of September's full moon. The harvest moon is the full moon that falls closest to the fall equinox, and it's associated with festivals celebrating the arrival of autumn. Here's what you need to know before catching the event this year.

What is a harvest moon?

You may have heard that the harvest moon is special because it appears larger and darker in the night sky. This may be true depending on what time of night you look at it, but these features are not unique to the harvest moon.

Throughout the year, the moon rises on average 50 minutes later each night than it did the night before. This window shrinks in the days surrounding the fall equinox. In mid-latitudes, the moon will rise over the horizon only 25 minutes to 30 minutes later night after night. This means the moonrise will occur around sunset several evenings in a row.

So what does this mean for the harvest moon? If you're already watching the sunset and you catch the moonrise at the same time, it will appear bigger than usual thanks to something called the moon illusion. It may also take on an orange-y hue because you're gazing at it through the thick filter of the Earth's atmosphere, which absorbs blue light and projects red light. So if you've only seen the full harvest moon around sunset, you may think it always looks especially big and orange, while in reality, any full moon will look that way when it's just above the horizon.

When to See the Harvest Moon

This year, the harvest moon will be visible the night of Saturday, September 14—about a week before the fall equinox on September 23. The moon will reach its fullest state at 12:33 a.m. ET—but if you're still convinced it's not a true harvest moon without that pumpkin-orange color, you can look for it at moonrise at 7:33 p.m. on September 13.

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