Leonid meteors. Optical time-exposure image of Leonid meteors (diagonal streaks) and star trails (curved tracks) over trees. Meteors, or shooting stars, are tiny dust particles which enter the Earth's atmosphere at high speeds. They are heated by air resistance, making them visible as streaks of light. The Leonid shower occurs annually for about 2 days around 17th November, when the Earth crosses the debris produced by the comet Tempel- Tuttle (55P). Star trails are produced on long- exposure photographs by the apparent motion of the stars caused by the Earth's rotation. Photographed in 2001.