Sky Watch: Falling stars from Perseus

The Perseid shower occurs in August when the Earth slams into the dusty debris expelled by Comet Swift-Tuttle. As this cometary litter plows into our upper atmosphere, it is incinerated and produces meteors. Most are specks no larger than a grain of sand and are extinguished at heights of 50 miles or higher.

During any meteor shower you'll see meteors (also called falling or shooting stars) all over the sky but, if you trace their paths backward, you'll discover that they all appear to come from one specific location in the sky. This is called the shower's "radiant" and is often named for the constellation in which it lies. This month's shower is known as the Perseids because its radiant lies in the direction of the constellation Perseus. Any that appear not to radiate from this direction are called "sporadic" meteors, and are flecks of dust not part of the Swift-Tuttle swarm.

This year's peak occurs during the moonless night of Wednesday and the morning of Thursday. Typically, we spot meteors before dawn because during those hours we face the direction of our planet's motion and can watch as we sweep up meteoric particles. During peak hours, stargazers under a dark sky could count as many as 60-100 every hour - all appearing to come from the direction of the constellation Perseus in the northeast.

For the best view, camp in the mountains or country, or set up on rural roads. You can watch the shower with just your eyes, but binoculars might help check out smoke trails left behind by any exploding fireballs. Take a lawn chair or sleeping bag and gaze toward the northern and northeastern sky.