The Naturalist's Corner: Bad moon ‘risinWritten by Don Hendershot
When we headed for the car after a glorious Thanksgiving dinner, the skies above Jonathan Creek were dark and clear, and the blue stars seemed close enough to touch. I could see Orion and the Pleiades and a couple of the brighter stars of Gemini, plus the big and little dippers. Of course there was much more to see, but without a star chart that was about as far as I could go.
However, looking up at the heavens in the crisp, late November evening reminded me that it wouldn’t be long till the Geminid meteor shower. The Geminids are probably the most reliable and showiest of the regular meteor showers. At its peak, the Geminid shower is blasting more than a fireball a minute through the firmament. This year’s Geminids start on Dec. 6 and go through Dec. 18, with peak being the late night and pre-dawn morning of Dec. 13 and 14.
Ah, I can picture it now. Some lawn chairs and blankets, a secluded area away from light pollution, a nice dark night — wait, what’s this? It’s like daylight. It’s a full moon. It’s not just a full moon. It’s the biggest, baddest full moon in 15 years, dashing the best laid plans of mice and men and amateur astronomers.
Any full moon puts a definite damper on meteor watching. But the full moon of Friday, Dec. 12 is not just any full moon. This full moon coincides with the moon’s perigee — the point in the moon’s orbit when it is closest to earth. On Dec. 12 the moon will be less than 222,000 miles away — just a cosmic fingertip.
The fact the moon will be full at its perigee brings it closer. When the moon is full, the moon, earth and sun are in line in space, and the tug from the sun’s gravitational field stretches the moon’s orbit a bit, bringing it closer to earth. It will be eight years before the moon passes this close again. And, on that day — Nov. 14, 2016 — the moon will once again be full.
It’s no accident that these close encounters of the lunar kind occur from late fall through early winter. The earth and sun are always closest around New Year’s Day. So any time the perigee and full moon occur simultaneously near the end or beginning of the year, the proximity of the sun draws Luna nearer.
This biggest baddest moon will bring with it this year’s biggest baddest tide. The closest perigee of the year, which this will be, is called the proxigee. The associated tide is known as the proxigean tide. The proxigean is the highest of high tides.
So it might not be a great night for looking at meteors, but it should be a great night for moon gazing — just don’t set up camp too near the ocean.