By Mike Lynch
No doubt you probably already heard or read that this weekend the full moon shining in our August skies is a “Super Moon”. Up until the last few years most people had never even heard of that term before, including yours truly. The term was actually coined by Richard Nolle, a famous astrologer, making it much more a term and tool of the practice of astrology and horoscopes than that of the science of astronomy. That’s why a lot of us haven’t heard the super moon moniker until recently. That sure has changed though as it’s become a new media darling buzz term. In fact some sources now say it’s possible to have multiple super moons in one year. Now I’m not necessarily against it and I don’t want to be a Johnny Buzzkill, but in all honesty a super moon is not all that super but I feel you should really know the whole story.
Without a doubt the full moon we see this weekend over Everett is the biggest full moon in our sky in 2014. That’s because it’s the closest full moon. Every 27.3 days the moon makes one complete orbit around the Earth. The moon has no light of its own but merely reflects the sun’s light as it orbits Earth. The changing angle between the moon, Earth, and the sun is what causes the moon to go through its cycle of phase changes. Full moons occur when the Earth lies roughly in a line between the sun and moon, and the moon is fully bathed in the sun’s light from our view on Earth. What gives rise to the super moon is that the moon’s orbit around the Earth is not a perfect circle but a little oval-ish. That means the moon’s distance from Earth varies more than 25,000 miles in the course of its circuit. Every month the moon’s farthest distance from the Earth, dubbed apogee, is over 250,000 miles. The closest distance, called perigee, is a little over 225,000 miles.
Astronomically the full moon this month is known as a perigee moon as it just so happens this month our full moon is occurring really close to perigee making it the closest full moon of 2014. Without a doubt full moon this weekend will year will be the biggest full moon in our sky, but not all that much bigger. In fact, it will only be about seven percent larger than the average full moon and about fourteen percent brighter. At least in my book that’s not exactly what I would call “super”. Now if it was twenty percent bigger and forty percent brighter I think for sure you could call it super. The fact of the matter is that honestly most people can’t really tell the difference between an average full moon and the “super” moon. However, the power of suggestion can be very powerful! On one TV newscast on the night of a “super moon” the weather person said “Hey, did you see the super moon rise tonight? It was huge wasn’t it?” Hello! The moon and sun always seem much larger when they rise and set. It’s an optical illusion caused by our eyes and brains comparing celestial bodies with land objects. Again, forgive me if I’m being a buzz kill. I might get busted by the media hip police!
The closest full moon of the year does have a true physical effect on Earth, however. Ocean tides will be a little higher than they usually are during an average full moon because of the increased gravitational pull of the closer moon. It’s said that the full moon can make people a little crazy. Maybe because it’s closer and has a slightly stronger pull there might be a little more lunacy. Or it’s just a good excuse!
Speaking of buzz kill, it’s too bad we have a full moon starting out this week because one of the best meteor showersof the year, the Perseids, are peaking this week, especially Tuesday night and Wednesday, August 12 and 13th. That night the moon will still be full enough to washout the sky, making all but the brightest of the meteors virtually invisible. If we didn’t have the moon in the sky for the Perseids and you were fortunate enough to view them in theskies of the dark countryside you could easily see over 50 meteors an hour or more, especially from 1:00am to the start of morning twilight. I wouldn’t make a point of sitting out to watch for themthis year unless you like moon baths, but you may see at least some meteors or “shooting stars”.
The meteors in the Perseids and other meteor showers are produced by grains of dust and pebbles that slam into the Earth’s atmosphere and get incinerated by friction. Some of theparticles may approach the size of small walnuts.Most of the light we see from meteors is the result of the ionization or temporary destabilization of the column of air they’re plowing through at speeds that can be over 40 miles a second! The debris particles that produce meteor showers are left behind by comets that have passed by the Earth and our sun. Comets are basically dirty snow/ice balls that partially melt when they get close to the sun. Debris from these partially melted comets is left in their wake and gravity between the particles keeps the debris trail in tact.
The debris trail that causes the Perseids is Comet Swift-Tuttle that comes by this part of our solar system about every 130 years and was last by in 1992. There is some thought that Swift-Tuttle could possibly collide with the Earth in 2126, but that’s been played down by a lot of astronomers so beware, who knows what you might read about it on the internet!
The next decent meteor shower this year will be the Orionids that will peak on the night of October 22-23rd. The Orionids aren’t as prolific as the Perseids, but there won’t be a moon out that night so the Orionids will be left in the dark, which is good thing!
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications available at bookstores at http://www.adventurepublications.net