A great summer shower
The annual Perseid meteor shower is a late summer stargazing classic in our Marshall skies. The Perseids this week, and the Geminids in December, are the two best annual meteor showers that we have. There are many other moderate to minor meteor showers that I believe get a little too hyped up by the media and the Internet, and I’m afraid folks get disappointed and discouraged when they lose sleep over not much of a show. The Perseids, though, will not let you down, especially this year because moonlight won’t get in the way at all during the peak next weekend.
The Perseids have actually been going on for about a week now, but the meteor shower will be peaking next weekend, Aug. 11-12, as well as Monday morning, Aug. 13. The best time to see the Perseids is after midnight and especially from 2 a.m. to 5 a.m. Get your afternoon nap! The Perseids are extra special this year because there’s no moonlight interference in the early morning hours, leaving us with dark skies. If you can get out into the countryside or at least the outer ring of suburbs for the really dark skies, all the better. You may see 50 to 80 or more meteors or “shooting stars” an hour. Maybe more than one every minute! Even in more lit urban areas you’ll see at least five to 10 an hour with a little perseverance.
Meteors in meteor showers like the Perseids are caused by small debris getting incinerated high in our atmosphere due to extreme air friction. The debris is usually the size of grains of dust, but some of the debris may be as large as walnuts. In most cases this debris is 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 too close to the sun. Debris from these partially melted comets is left in their wake, and gravity between the particles keeps the debris trail intact. Meteors from meteor showers are best seen after midnight because we are then on the side of the Earth heading into the debris trail. See the diagram.
The debris trail that causes the Perseids is from comet Swift-Tuttle, which visits 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 … stay tuned though!
In the meantime, tiny pieces of comet Swift Tuttle will slam into our atmosphere at speeds over 40 miles a second; easily incinerating them before they can get anywhere near you. Most of the light you see from meteors as they streak across the sky is not caused by their flaming death, however, but by ionization. These debris particles are zipping through our atmosphere so fast that the column of air they are going through is being destabilized. Zillions of electrons are temporarily bounced away from the nucleus of zillions and zillions of atoms, and that produces energy in the form of light. Meteors come in different colors as well, depending on what kind of atmospheric gases they go through. I’ve seen just about all the colors in the rainbow. Many of them change colors as they rip across the sky.
The Perseids are called the Perseids because all of the meteors seem to emanate from the general direction of the constellation Perseus the Hero. Perseus rises high in the northeastern sky in the early morning hours. Does that mean you just look toward the northeastern sky? Absolutely not! If you do you’ll miss a lot of meteors. My advice for watching the Perseids, or any other meteor shower, is to lie back on the ground or a reclining lawn chair and roll your eyes all around the sky. Watching a meteor shower with family and/or friends is a lot of fun because you have that many more eyes watching the big sky. This is all the more reason to plan a Perseid campout party. It’s possible you could see two meteors every minute in the early morning hours. You have to be attentive and diligent because while the Perseids are famous for the number of meteors you may see, many of them are faint and rip across the sky rapidly.
While you’re watching for the Perseids you can also enjoy the great show being put on by the planet Mars. It will be out all night long, not setting in the southwest until morning twilight. It’s the closest and brightest Mars has been to us since 2003. Even with a small to moderate telescope you can see some of the surface features like its extensive valleys and even it the southern polar cap, which will be located toward the upper limb of the planet if your telescope gives you an upside down reverse image like most do.
Don’t forget the bug juice and have fun with the Perseids!
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and at adventurepublications.net.