You have probably heard that this Sunday’s full moon will bring the biggest and brightest of the year so far. This is because December 3’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 happens when a full moon coincides with the perigee of the moon’s orbital cycle. The perigee is the point at which the moon moves closest to the 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 moon appear larger in the sky, allowing it to reflect more light and look brighter.
What’s cool about this one?
This weekend offers the first and only supermoon of the year. It should shine 16 percent brighter and seven 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. Star gazers will be able to catch this occultation from some parts of the U.S., Canada, Russia and even Bangladesh, Space.com reports.
How can I see it?
The best time to see a supermoon is just after sunset. Something called the “moon illusion” will make 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 is probably something to do with our eyes. NASA has this handy hack so you can prove it’s just an illusion yourself.
As you might expect, it’s also a good idea to get as far away from ambient light as possible to get the clearest view.
For budding astronomers living in the mainland U.S., the supermoon will rise at 4:29pm local time in San Francisco and 5:26pm in New York City. If you are in Honolulu, head outside from 6:25pm. Alaskans based in Anchorage can catch the moonrise at 4:28pm.
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 4:00am ET.
To record the supermoon, NASA recommends 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 these 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 can also be 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 the agricultural and hunting calendars.
September’s Harvest Moon coincides with—you’ve guessed it—autumn’s traditional gathering of crops. Some 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 mid-winter.
Last month’s Beaver Moon reflects 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 dazzle star gazers with some spectacular celestial events. Be sure to head to 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 of supermoons in 2017, but January alone will offer two. Spot the Wolf Moon on January 2 and a rare ‘blue’ supermoon on January 31.