Leonid meteors. Optical time-exposure image of Leonid meteors (green/white streaks) against a starfield. 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). The meteors all seem to originate from one point in the sky (the radiant, lower left). This is an effect of perspective: the meteors actually all have parallel tracks. The bright object at upper left is the planet Jupiter. Photographed in 2001.