If your local weather cooperates very early Friday morning, look up towards the constellation Perseus. That’s because August 12 is the expected peak of the Perseid meteor shower, traditionally one of the best celestial shows of the year. But this year’s Perseids are expected to dazzle even more than they usually do.
Why? Earth’s orbit around the sun is expected to take it through at least three streams of leftover debris from the comet Swift-Tuttle, astronomers say. That’s the source of the Perseids, and if things go right, lucky stargazers will get an opportunity to see as many as 200 meteors per hour.
The last time the Perseids were this good was in 2009, when for a brief period rates soared above 170 meteors per hour. This year’s version has the potential to be even bigger, and that’s got the astronomy community buzzing. “Forecasters are predicting a Perseid outburst this year with double normal rates on the night of Aug. 11-12,” NASA meteor researcher Bill Cooke says.
Helping to make this show even better is Jupiter. The gas giant’s gravity tugs on the meteor stream just enough some years to put Earth in the center of the stream, which causes a brief but dramatic upswing in the meteor count as the peak approaches.
Most of these meteors are tiny though, posing no threat to us here on the ground. However their breakneck speed — some 132,000 miles per hour — causes even tiny specks of dust to illuminate as they reach temperatures upward of 10,000 degrees fahrenheit during entry into our atmosphere.
You can tell what the meteor’s made of by the color of its trail: orange-yellow is typically sodium, yellow is iron, blue-green is magnesium, violet is calcium, and reds are caused by nitrogen and oxygen. In the right conditions, meteor showers like what’s expected Friday morning can be pretty cool.
But like weather, predicting meteor showers is an imperfect science. Minor miscalculations in where the meteor streams can mess everything up. There have been years where the Perseids have disappointed from time to time, and issues such as cloud cover and light pollution also pose a problem.
Most locations across the United States should have decent weather tonight and Friday morning. While cloud cover may obscure some of the meteors east of the Mississippi (especially across the Mid-Atlantic and the Great Lakes), most western locales will have almost or completely cloud-free skies to enjoy the show. Those in the Plains and Rocky Mountain states might also have to deal with periods of cloudiness from time to time.
As for light pollution, you’re going to want to get as far away from urbanized areas as possible, otherwise you’ll miss a lot of the smaller meteors. Also keep in mind you’ll need to give your own eyes about 20 minutes to fully adjust to the lower light.
As for whether or not it will live up to expectations, current counts are promising: some observers saw as many as 45 meteors an hour in Europe this evening, with the peak still a half a day off, or sunrise Friday on the east coast. Meteor showers typically have a sharp peak when it comes to per hour rates, so the highest counts will be seen in a relatively small area, this time the Western US. But it is happening, and at worst it will still live up to our expectations of the Perseids in any other year.
Updated on 8-11-2016 by Ed Oswald: new weather forecast information and current meteor count.