A meteor shower occurs when Earth crosses the path of a comet. Comets leave behind many small particles, flecks of rock shed by the comet’s evaporating ices that are moving about 44 miles per second. They are usually smaller than an appleseed. As the small particles enter Earth’s atmosphere, the friction heats the particle and surrounding air until it incandesces, or glows. That’s what we see streaking a trail of light across the sky.

Most particles burn up and never reach the ground. Occasionally, a particle may be large enough to reach the surface of Earth. Two orbiting satellites have been disabled during a meteor shower. The roofs of two homes in Wethersfield, Connecticut, were punctured in 1971 and 1982. In 1992, a car in New York was totaled when a meteor went through its trunk. The meteor was found underneath the car. Nobody was injured in any of these events. The danger during a meteor storm is extremely small.

The Leonid meteor shower occurs every November 18 when Earth crosses the dusty trail left by Comet Tempel-Tuttle. Every thirty-three years, Earth passes through the densest part of the comet’s trail, creating very active meteor showers. In 1833 and 1966, about forty meteors per second were seen for about an hour in the western states. Last year, the Leonids peaked over the Middle East countries, where thousands of meteors were visible.

The Leonid meteor shower peaks before dawn on November 18 this year. Peter Jenniskens of NASA’s Ames Research Center predicts the heaviest part of the shower will peak over the United States and Canada. There could be seven meteors per second visible in the sky for about two hours, which is about 4,000 meteors per hour visible shortly before dawn.