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Like all comets, Swift-Tuttle is a bit of a slob. As it loops around the Sun, some of its icy surface vaporizes, releasing bits of rock and dust into space. The comet dust spreads out along Swift-Tuttle’s orbit, forming clumps of debris.
That’s a good thing for those who like to watch the night sky, because those clumps turn into the Perseid meteor shower, which is underway for the next few nights.
Every year at this time, Earth crosses the comet’s orbit. Grains of dust streak into the atmosphere at tens of thousands of miles an hour. They vaporize, forming the streaks of light known as meteors or shooting stars.
Just how many meteors will streak across the sky in a given year depends in large part on where Swift-Tuttle is. More material congregates near the comet, so the Perseids are better when Swift-Tuttle is close by.
It was closest to the Sun in the early 1990s, so the Perseids put on some great displays back then. But today, the comet is far away from the Sun, and the stream of comet dust is thinning out, so the Perseids aren’t quite as busy.
Even in down years, though, the Perseids put on a pretty good show. This year, for example, you might see a couple of dozen meteors per hour. The view is enhanced because the Moon is a thin crescent, and it doesn’t rise until a couple of hours before dawn. With no moonlight to overpower the faint meteors, the Perseids are well worth a try.
We’ll have more about the Perseids tomorrow.
Script by Damond Benningfield, Copyright 2015