The Perseid meteor shower … plowing through the comet debris
All of us living on this big world are tearing around the sun at a speed of more than 67,000 mph. This month, as our Earth continues its orbit around the sun, we’re running into a dust debris trail left behind by a comet. This cosmic trash is courtesy of Comet Swift-Tuttle that last invaded our part of the solar system in 1992. All comets are basically dirty snowballs that turn into litterbugs as they partially melt and leave behind trails of dust and debris no bigger than pebbles. When the Earth runs into these trails we get a meteor shower as some of the debris gets gravitationally sucked into our atmosphere. Air friction then goes to work and 99.9% of the debris gets completely incinerated at an altitude of 50 to 75 miles above our heads.
The meteor shower lighting up our Marshall skies through this week is one of the best of the year. It’s the annual Perseid meteor shower. Most would agree that it’s certainly the most weather friendly meteor shower. You can stay out all night long under the stars and see more meteors after midnight when you’re on the side of the Earth that’s heading into the Swift-Tuttle Comet debris. Before midnight you’re facing the other way in space, but after midnight our part of Earth will have rotated in the direction of Earth’s orbit around the sun. It’s just like taking a drive after dark in the countryside. You’re going to get more dead bugs on your front windshield than you will on your rear window.
The very best morning this week for the Perseids will be this coming Wednesday morning, Aug. 13, from 1 a.m. to the start of morning twilight. That’s when the Earth will be in the thickest part of the debris trail. There is a hitch this year for the Perseids, however. It’s moonlight.
Unfortunately the moon will be nearly full this coming Wednesday morning after midnight, and the abundance of lunar light is really going to whitewash the sky, camouflaging all but the brighter meteors. All is not lost though, because on the morning of Aug. 13 the nearly full moon sets below the southwest horizon by 3:30 a.m., leaving almost two hours of darker skies. That’s good timing since that’s often when you see the most meteors.
If you can, view the Perseid meteor shower away from heavy city lights in the countryside. Even in areas with limited dark skies you may see 50 meteors an hour, and maybe as many as 100 an hour! If you’re forced by time and work constraints to view the Perseids in a moderately light polluted sky, you should still be able to spot at least 10 to 20 an hour if you do it right. The best way to watch the Perseids is to lie back on a blanket on the ground or a reclining lawn chair and roll your eyes all around the sky, slightly favoring the high northeastern sky.
If I were you I wouldn’t wait until the peak of the Perseids. If possible, start watching for meteors early tomorrow morning in the hours before twilight. While you probably won’t see as many meteors the moonsets will be a little earlier, leaving you with a longer stretch of darker skies. You’ll also have an insurance policy if it’s cloudy the morning of Aug. 13.
It’s called the Perseid meteor shower because the meteors seem to emanate from the general direction of the constellation Perseus the Hero, which is in the high northeast sky in the predawn hours. You can pull up a sky chart on my website lynchandthestars.com or on apps like Skyguide or Stellarium to see exactly where to locate Perseus, but that’s not all that important. Again, I advise you to roll your eyes all around the heavens, because if you restrict your gaze to just the area around Perseus you’re bound to miss meteors. They seem to come from the general direction of Perseus but they pop up throughout the celestial dome. The more people you have watching with you the more you’ll collectively see. All you need are your naked eyes (with eyeglasses if necessary). Binoculars or a telescope are no good with meteor showers because they can only zero in on a very small area of the sky. You need to see the “big picture.”
The dust particle to pebble size ammunition from this meteor shower incinerates over your head because of extreme air friction, but the light you’re seeing is not because of combustion. This makes perfect sense, because how could a tiny little speck burn up at 50 to 75 miles high? The light produced as these meteors streak into our atmosphere at over 130,000 miles a second, way faster than a bullet out of a gun, is because of photochemical reactions. These particles are ripping through their respective columns of air so fast that the atoms and molecules in those columns are temporarily destabilized, producing the light that we see. Meteors can be all different colors, but the disrupted nitrogen and oxygen atoms in our atmosphere a produce a lot of blue and green tinges in the quick streaks across the heavens.
Pray for clear skies this week and enjoy the Perseids. They’re worth waking up early for!
Celestial hugging this weekend: The near full moon will be closely passing by the bright planet Saturn and the constellation Sagittarius the Archer this weekend. Saturn’s around 850 million miles away from Earth and even with a small telescope you can see Saturn’s ring system.
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.