Perseid meteor shower. Optical image of a meteor track (upper right) from the Perseid meteor shower. This shower reaches its peak around August the 12th each year, but its meteors may be seen for about three weeks around this date. Meteor tracks, also known as falling or shooting stars, are caused by tiny dust grains entering the Earth's atmosphere. The air resistance incandesces the particles making them visible as streaks of light. Meteor showers occur regularly each year when the Earth crosses the orbit of a comet and its debris enters into the atmosphere. The Perseid shower is associated with the Swift-Tuttle comet. This image was taken near the 2007 peak.