Perseids << PUR see ihds >> is the name for a meteor shower that occurs around mid-July to mid-August each year. A meteor is a streak of light that appears in the sky when a piece of matter enters Earth’s atmosphere from space at high speed. Such a piece of matter is called a meteoroid. Meteor showers occur when Earth travels through a stream of meteoroids. Annual meteor showers occur when Earth moves through a certain stream during the same span of days or weeks each year.
The point in the sky from which the meteors appear to originate, called the radiant, lies in the direction of the constellation Perseus in the northern sky. However, the constellation is not the source of the meteors. The Perseids are among the most spectacular annual meteor showers. During the peak, around mid-August, 50 to 100 meteors may be seen streaking through the sky every hour.
The meteoroids that create the Perseids originate from a stream of dust and debris in the path of comet Swift-Tuttle. The comet was first observed independently by the American astronomers Lewis Swift and Horace Tuttle in 1862. Earth crosses the orbital path of this comet every year. In 1867, the Italian astronomer Giovanni Schiaparelli determined that debris from this comet was the source of the Perseids. Comet Swift-Tuttle completes an orbit of the sun every 133 years. The comet last reached perihelion–its closest approach to the sun–in 1992.
