Perseid Meteor Shower
by Nick Strobel
The famous Perseid meteor shower is expected to "peak" (largest number of meteors per hour) the night of August 12th/13th. The Perseid meteor shower happens when the Earth runs into the dust trail left behind by Comet Swift-Tuttle. The bits of comet debris hit our atmosphere at 38 miles/second (61 kilometers/second) and burn up above the stratosphere several tens of miles above the ground. Because the Earth is plowing into Comet Swift-Tuttle's dust trail, the meteors appear to streak out of a particular direction in space in the constellation Perseus. That point in Perseus will rise around 9:45 PM but more meteors should be seen after midnight because the California part of the Earth is facing the direction of the Earth's orbital motion around the Sun (see the diagram below). Comet bits moving at any speed can hit our atmosphere. Before midnight, the California part of the Earth is facing away from the direction of orbital motion, so only the fastest moving comet bits can catch up to the Earth and hit the atmosphere. The same sort of effect explains why your car's front windshield will get plastered with insects while the rear window stays clean.
Where to go? Somewhere far from city lights is best! At least 20 miles outside the city and preferably out of the valley and its dusty air. Members of the local astronomy club, the Kern Astronomical Society, usually gather at their Lockwood site off of Forest Service route 8N04 (see website for a map) for viewing the Perseids.
No binoculars or telescope are needed. In fact, you will miss most (or all!) of the meteors if you use them because binoculars and telescopes zoom in on one small piece of the sky. The meteor streaks will cover a broader piece of the sky than the widest field possible with binoculars. Also, you will see more meteor streaks out of the corner of your eye because your eyes have greater light sensitivity around the periphery of your vision than in the center.
The best years for the Perseids are when the Moon is near New Moon phase, so check my Night Sky column to see if this year is one of the good ones. Although the peak of the Perseids is on the night of the 12th/13th, the dust trail of Comet Swift-Tuttle is pretty broad so the number of meteors/hour has been increasing for several nights before the 12th and will gradually fall off over the next several nights after the 13th.
Can't make it out of the city? Still give it a try because the Perseids can sometimes have some especially bright meteors---bright enough to make even the most experienced observers exclaim, "Wow!"
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com