Skywatch: A great summer shower

The annual Perseid meteor shower is a late summer stargazing classic in our Minnesota-Wisconsin skies. The Perseids, which peak this week, and the Geminids in mid-December, are the two best annual meteor showers in our skies. Many other moderate to minor meteor showers get too overhyped by the media and the internet. 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 since moonlight won’t get in the way during the peak next weekend.

The Perseids have been going on for about a week and will continue this week, peaking next weekend, Aug. 12-13. The best time to see the Perseids, or any meteor shower, is from around midnight to just before morning twilight gets going. 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 to the outer ring of suburbs for the especially 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 bit of perseverance.

Meteors in meteor showers like the Perseids are caused by small debris getting incinerated high in our atmosphere because of 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 dirty balls of snow and ice that partially melt when they get too close to the sun. Debris from these partially melted comets gets left in their wake, and gravity between the particles keeps the debris trail intact. Meteor showers are best seen after midnight because we are on the side of the Earth heading into the debris trail, as you can see in 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. It last passed by us in 1992.

Tiny pieces of comet Swift-Tuttle 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 but by ionization. These debris particles are zipping through our atmosphere so fast that the air they are going through is temporarily destabilized. Zillions of electrons are temporarily bounced away from the nucleus of zillions of atoms. That produces energy in the form of light. Meteors also come in different colors, 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.

This meteor shower is 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 northeast 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 friends is fun because you have many more eyes watching the big sky. This is all the more reason to plan a Perseid campout party. Seeing two meteors every minute in the early morning is possible. You must be attentive and diligent because while the Perseids are famous for the number of meteors you may see, many are faint and rip across the sky rapidly.

Remember the bug juice, and have fun with the Perseids!

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Mike is available for private star parties. You can contact him at [email protected].

Friday, Aug. 18, 8:30-10:30pm, Camden State Park near Lynd, Minn. For more information, call 507-872-7031 or visit www.dnr.state.mn.us/state_parks/park.html?id=spk00127#homepage

Saturday, Aug. 19, 8:30-10:30pm, Lake Shetek State Park near Currie, Minn. For more information, call 507-872-7031 or visit www.dnr.state.mn.us/state_parks/lake_shetek/index.html

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