Perseid meteor shower set to dazzle


By David Shiga (Image: Jimmy Westlake) Tuesday morning will provide one of the year’s best opportunities to see some “shooting stars”, with the peak of the annual Perseid meteor display. Meteors are bits of dust or rock that plunge into Earth’s atmosphere at high speed, producing a glowing trail when they excite gas particles. On any clear night, a handful of meteors can be seen per hour, but that rises to dozens per hour during a meteor shower. The Perseid meteor shower is one of the best annual displays and is best seen from the northern hemisphere. From a dark site, far from city lights, viewers should be able to catch around 60 meteors per hour at the peak. For observers at most locations, the peak will arrive in the early morning hours on Tuesday, local time, before dawn breaks. Smaller numbers of meteors will be visible on Monday evening, since light from a nearly full Moon will wash out fainter meteors. The number of meteors visible will increase when the Moon sets at around 0130 local time on Tuesday for observers at mid-northern latitudes. The meteors will appear all over the sky, so the best strategy is to lie down and stare at as large a patch of sky as possible – away from the Moon, if it is still up. Tracing the paths of the meteors backwards will lead to a point in the constellation Perseus, which gives the yearly display its name (scroll down for image). Perseid meteors are bits of debris shed by comet Swift-Tuttle, which takes 133 years to orbit the Sun and last passed through the inner solar system in 1992. Its fragments hit the atmosphere at an average speed of 59 kilometres per second, causing most to disintegrate far above Earth, at altitudes of 80 to 120 kilometres – around the edge of space at 100 km. A typical meteor barrelling through the thin atmosphere at this height is just the size of a grain of sand or a small pebble. But it creates a column of glowing gas tens of kilometres long and hundreds of metres wide. Earth accumulates an estimated 1000 to 10,000 tonnes of material from meteorites each day. Comets and Asteroids – Learn more in our special report. More on these topics:
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