A Perseid meteor streaks across the northern sky. The Perseids, an annual meteor shower, is already upon us. Reelika Saar
It’s that time again. Every August the Earth sails through crumbs dropped by comet Swift-Tuttle. The same way you cross an intersecting street on your way to the store, Earth crosses through the orbital trail of debris left by repeated returns of the comet to the inner solar system. During each visit, solar heating vaporizes a portion of the comet’s dust-embedded ice. Poof goes the ice, but the dust remains and spreads out along Swift-Tuttle’s orbit to become the Perseid meteor shower.
Earth plows through the material, which ranges in size from sand grains to small pebbles. When the bits strike the atmosphere they’re moving at around 37 miles a second (59 km/sec) but come to as sudden skid as they buck up against the air. That raises their temperature to a couple thousand degrees. The particles burn to a fine soot but pass on their kinetic energy (energy of motion) to the air.
The Perseids appear to stream from the constellation Perseus just beneath the W of Cassiopeia from a point called the radiant. The map shows the sky ...