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

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.)

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Space
The Fascinating Device Astronauts Use to Weigh Themselves in Space

Most every scale on Earth, from the kind bakers use to measure ingredients to those doctors use to weigh patients, depends on gravity to function. Weight, after all, is just the mass of an object times the acceleration of gravity that’s pushing it toward Earth. That means astronauts have to use unconventional tools when recording changes to their bodies in space, as SciShow explains in the video below.

While weight as we know it technically doesn’t exist in zero-gravity conditions, mass does. Living in space can have drastic effects on a person’s body, and measuring mass is one way to keep track of these changes.

In place of a scale, NASA astronauts use something called a Space Linear Acceleration Mass Measurement Device (SLAMMD) to “weigh” themselves. Once they mount the pogo stick-like contraption it moves them a meter using a built-in spring. Heavier passengers take longer to drag, while a SLAMMD with no passenger at all takes the least time to move. Using the amount of time it takes to cover a meter, the machine can calculate the mass of the person riding it.

Measuring weight isn’t the only everyday activity that’s complicated in space. Astronauts have been forced to develop clever ways to brush their teeth, clip their nails, and even sleep without gravity.

[h/t SciShow]

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Watch Astronauts Assemble Pizza in Space
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iStock

Most everyone enjoys a good pizza party: Even astronauts living aboard the International Space Station.

As this video from NASA shows, assembling pizza in zero gravity is not only possible, it also has delicious results. The inspiration for the pizza feast came from Paolo Nespoli, an Italian astronaut who was craving one of his home country’s national dishes while working on the ISS. NASA’s program manager for the space station, Kirk Shireman, sympathized with his colleague and ordered pizzas to be delivered to the station.

NASA took a little longer responding to the request than your typical corner pizzeria might. The pizzas were delivered via the Orbital ATK capsule, and once they arrived, the ingredients had to be assembled by hand. The components didn’t differ too much from regular pizzas on Earth: Flatbread, tomato sauce, and cheese served as the base, and pepperoni, pesto, olives, and anchovy paste made up the toppings. Before heating them up, the astronauts had some fun with their creations, twirling them around like "flying saucers of the edible kind,” according to astronaut Randy Bresnik.

In case the pizza party wasn’t already a success, it also coincided with movie night on the International Space Station.

[h/t KHQ Q6]

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