Want to see August's super-blue-moon? Or just know what it is?

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Look! Up in the sky! It’s the moon! It’s a supermoon! It’s superbluemoon!

August brings its share of astronomical wonders. Some of them — like the Perseid meteor shower on Aug. 13, or the Kappa Cygnid shower five days later — are annual events. Others, such as two supermoons and a blue moon, happen at various times of the year.

What’s a supermoon?

It’s not an official astronomical term. In fact, it was coined by an astrologer, Richard Nolle, in 1979, to refer to a full moon that takes place while the moon is near its closest point to the Earth. If you want the fancy astronomy term, it’s a perigee-syzygy of the Earth/moon/sun.

Like all astronomical bodies, the moon orbits in an ellipsis that takes it from about 360,000 km away from the Earth (perigee) to about 405,000 km away (apogee). The difference means that a full moon at perigee can look 14 per cent bigger and about 30 per cent brighter than one at perigee.

The moon reaches its closest point to the Earth on Aug. 2, and again on Aug. 30. That’s close enough to the full moons of Aug. 1 and Aug. 31 to make them supermoons. They’re easy to see, rising shortly after sunset all across Canada.

While beautiful, supermoons are not much more spectacular than regular full moons – any videos you’ve seen online of the moon filling half the sky are just hokum. And while Nolle notes that the Christchurch earthquake, Hurricane Katrina and the Mt. Pinatubo eruption all took place on (or near) a supermoon – well, that’s what’s known as a super coincidence.

So what’s a blue moon?

This is another non-astronomical term, and refers to the second full moon in a calendar month. Since it takes about 29.5 days to go from one full moon to the next, every month (except February) can have a second full moon if the first one arrives in the first day or two. (It’s not actually blue, however.)

According to the Encyclopedia Brittanica, the term “blue moon” started being used in the early 1900s to refer to a fourth full moon in any three-month season. Then in 1946, an article in Sky & Telescope magazine mistook it to mean the second full moon in a month, and that definition stuck.

The phrase “once in a blue moon” refers to something very rare, but blue moons aren’t super-rare, averaging out to one every 33 months, or 41 times a century. That said, 2018 had a rare “double blue moon,” with a blue moon in January and another in March. The next time that happens will be in 2037. The next regular blue moon will be in May of 2026.

What about the Perseid meteor shower?

The Perseids, so named because the meteors seem to originate near the constellation Perseus in the northeast, is one of the brightest of the annual meteor showers. (It’s also one of the warmer-weather ones, as opposed to, say, the Geminids, which happen in mid-December.)

The meteors come from debris from comet Swift-Tuttle. Too small to reach the ground, they are nevertheless visible in numbers of up to one per minute, although the best viewing is as far from city lights as possible. Good news this year — peak activity is the night of Aug. 13, just three days before the new moon, meaning there won’t be much interference from the moon’s glow.

And the kappa Cygnids?

While the Perseids are a Class I meteor shower, producing tens of meteors (or more) every hour, Class II showers like the kappa Cygnids might max out at just five per hour. Still, if you’re outside in a dark place, it never hurts to look up.

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