Supermoon 2017: Everything You Need to Know About December's 'Full Cold Moon'

You have probably heard that this Sunday’s full moon will bring the biggest and brightest of the year so far. December 3rd’s "full cold moon" will be the only supermoon of 2017.

But what exactly is a supermoon, and why is everybody talking about it?

What is a supermoon?

A supermoon occurs when a full moon coincides with the perigee of the moon’s orbital cycle. A perigee is the point at which the moon moves closest to Earth during orbit. Because the orbit is not a perfect circle, this means the moon typically sits anywhere between 252,000 and 226,000 miles from Earth. That is a difference of 26,000 miles—longer than the entire circumference of the Earth.

The shorter distance makes the moon appear larger in the sky, allowing it to reflect more light and look brighter.

11_3_Supermoon A supermoon rises in Marseille, France, on November 14, 2016. BORIS HORVAT/AFP/Getty Images

What’s cool about this one?

This weekend offers the first and only supermoon of the year. It should shine 16 percent brighter and 7 percent larger than normal, reports National Geographic. However, this year may not be quite as bright as last November’s supermoon, which was the closest perigee in 68 years.

The moon will also pass in front of the bright star Aldebaran. Stargazers will be able to catch this occultation from some parts of the U.S., Canada, Russia and even Bangladesh, Space.com reported.

How can I see it?

The best time to see a supermoon is just after sunset. Something called the “moon illusion” makes the moon appear even bigger: The closer it is to the horizon, the larger it looks. No one knows exactly why this happens, but it probably has something to do with our eyes. NASA has this handy hack so you can prove it’s just an illusion.

As you might expect, it’s also a good idea to move as far away from ambient light as possible in order to get the clearest view.

12_1_Supermoon Sydney Bathed in the light of a supermoon, a man crosses Sydney Harbour Bridge on November 15, 2016. Jason Reed/Reuters

For budding astronomers living in the mainland United States, the supermoon will rise at 4:29 p.m. local time in San Francisco and 5:26 p.m. in New York City. If you are in Honolulu, head outside at 6:25 p.m. Those in Anchorage, Alaska, can catch the moonrise at 4:28 p.m.

If you want to catch the supermoon at its closest, you’ll need to get up really early (or stay up really late). The moon will reach just 222,443 miles from Earth at 4 a.m. ET.

To record the supermoon, NASA recommended fitting your camera with a telephoto lens. Lengthening the shutter time and increasing the ISO (sensitivity) can compensate for low light. You will need to keep an eye on those settings throughout the night, as the moon illusion, clouds and changing ambient light may affect your camera’s performance.

What does "full cold moon" mean?

This year’s supermoon is also called the full cold moon. This is because it is the first full moon of December, a sign that winter is here.

Humans around the world have used moons to track the passage of time for thousands of years. Different names for specific full moons often reflect important times in agricultural and hunting calendars. September’s harvest moon coincides with—you guessed it—autumn’s traditional gathering of crops.

Other names recognize the importance of animals throughout human history. January’s wolf moon is named after the sound of hungry wolves. Native Americans and medieval Europeans would recognize their howls as a sign of midwinter.

Last month’s beaver moon reflected the Algonquin tribe’s practice of setting traps for beavers. Catching the critters in November would bulk up your winter fur supply.

More than just the supermoon

The coming weeks are set to dazzle stargazers with some spectacular celestial events. Be sure to head for clear skies for the Geminid meteor shower on December 14, which will fill the sky with up to 120 meteors per hour. We may have been starved for supermoons in 2017, but January 2018 will offer two. Spot the wolf moon on January 2, and a rare, "blue" supermoon on January 31.

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