Les Perseids! They are called the sons of Perseus, for they appear to emanate from the Northern Hemisphere constellation of that name, given in honour of the Greek demi-god who dispatched Medusa and rescued Andromeda from a sea monster. Catholics, meanwhile, have called them the tears of St. Lawrence, owing to the fact that the peak of their brilliant spectacle occurs on or near Aug. 10, the date of that saint’s martyrdom. First recorded nearly 2,000 years ago, the Perseid meteor shower is an annual event, much heralded by astronomers, when Earth makes a five-week passage through the cloud of dust left by the tail of comet Swift-Tuttle, which circles our sun on the same trajectory once every 130 years. This year it will be most prolific on Sunday and Monday nights, when viewers may see as many as 60 to 100 “shooting stars” per hour. They’re not stars, of course, or planets, or anything as majestic even as a cosmic pebble from the beach of time. According to Charles Boyle, president of the Ottawa chapter of the Royal Astronomical Society of Canada, each glorious streak of light is caused by a piece of dust half the size of a grain or sand or smaller, burning up as it careens into Earth’s atmosphere at almost 60 kilometres per second. “It’s like skipping a rock off a wall, where you get a spark,” he says. “Well, here you get a bigger spark.” There are larger detonations, too, called fireballs, where massive particles the size of half a grain of rice are ignited, so bright that if you happen to be looking down at the ground when they explode 100 kilometres overhead, you’ll see your shadow. “It’s quite spectacular,” says Boyle, “and a nice summertime shower.”
Posted on: Sat, 10 Aug 2013 02:35:22 +0000
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