2017's only supermoon to occur on Sunday, December 3. Is it really that super?

Posted by Jake Parks
on Friday, December 1, 2017

The first and only supermoon of 2017 is scheduled to make its appearance on Sunday, December 3, 2017

Guest blog by Amber Jorgenson

If you check your celestial calendar, you’ll notice a pretty stellar galactic event is coming up this weekend. The only supermoon of 2017 is scheduled to descend upon the sky on Sunday, December 3. Though they have been non-existent in 2017 thus far, two more supermoons are set to follow in January 2018. With the surge of supermoons in the coming months, people may be wondering what’s so super about them anyway, and if they’re worth keeping an eye out for. To help answer these questions, we’ve featured some basic information about supermoons to help you make your choice.

What is a supermoon?

A supermoon is a brighter, larger version of the full moon that comes around every orbital period. Your average full moon occurs when the Moon is in line with the Earth on the opposite side of the Sun. When the three masses line up, the sunlight reflecting off of the Moon give us the full moon view. What differentiates a supermoon from a not-so-super moon is its position in orbit. The moon orbits the Earth in an ellipse, as opposed to a flawless circle. Because of this, the distance between the Earth and the Moon is constantly varying. The apogee refers to the furthest distance that the Moon is away from the Earth during orbit, usually about 251,966 miles (405,500 kilometers). When the Moon is closest to Earth in orbit, it is referred to as the perigee, with a distance of about 225,744 miles (363,300 kilometers) between the two. The Moon will always reach the perigee and the apogee during its 27-day cycle.

Though the term supermoon does not have an official astronomical definition, full moons generally fall into the supermoon classification if they are 90 percent or closer to the perigee. To sum it up, if the day when the Moon is in perigee lines up with its full moon, a supermoon is designated. I’ll leave it up to you to determine just how “super” the celestial coincidence is.

So, just how visually different is a supermoon compared to a regular full moon?

Being that the Moon is closer to the Earth during a supermoon, two things happen that impact its appearance. It’s pretty basic knowledge that when an object is closer, it will appear larger. Due to its closer proximity to Earth, a supermoon can appear as much as 14 percent larger in diameter than the smallest full moons that appear in the sky. So, unless you have a rather vivid memory, the increase in size may be negligible to the naked eye. The difference that you’re more likely to notice is the brightness of the supermoon. Since it is in perigee, the sunlight that reflects off of the Moon will appear more abundant, causing the Moon to appear up to 30 percent brighter.

What are the best conditions to see the supermoon?

Since the planetary wonders can often be disguised by light pollution, it’s a good idea to escape any city lights and venture out to no-man’s-land for the clearest view. As for the time of day, try checking it out around your local moonrise time. Although it has been proven that the Moon appearing larger during this time of the day is an illusion, we can ignore logical thought for the day and give in to the visual misconception.

Is it worth taking a look at?

I can’t think of a logical reason not to. Whether you are well versed in the study of astronomy, or just a stargazer wanting to catch a glimpse of the seemingly brighter and larger Moon, I couldn’t imagine taking a glance would hurt. But hey, I’ll leave it up to you to determine just how super the supermoon is. 

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