Friday, August 14, 2015

Perseid Meteor Shower Puts on a Spectacular Show

Perseid meteors seen over Bergen, Norway on Aug. 13, 2015. Credit: Ronny Tertnes

In the Northern Hemisphere, the annual August Perseid meteor shower, that peaked on Wednesday night, probably ranks as the all-time favorite meteor shower of the year. The moon posed no obstacle this year, giving some skywatchers the best views of shooting stars in years — even in areas that usually have too much light for skywatchers to see anything. The annual Perseid shower occurs when pieces of comet Swift-Tuttle hit Earth's atmosphere at more than 133,000 mph and burn up. It is the oldest know meteor shower.

The bits and pieces from Comet Swift-Tuttle slam into the Earth’s upper atmosphere, lighting up the nighttime with fast-moving Perseid meteors. If our planet happens to pass through an unusually dense clump of meteoroids – comet rubble – we see an elevated number of meteors.

The highest concentration of meteors was visible on Thursday after 3 a.m. local time around the world, although it was possible to catch a glimpse beforehand, starting at around 11 p.m.

The Perseids are one of the most plentiful showers (50-100 meteors seen per hour) and occurs with warm summer nighttime weather, allowing sky watchers to easily view the shower.

"The Perseids are usually fairly bright. Also, they tend to leave a trail, or train, behind them. You can see the train hanging there glowing in the sky for a few seconds - sometimes for several minutes - after the meteor has gone," said Robin Scagell, vice president of the Society for Popular Astronomy.

Perseid meteors seen over Allgood, Alabama on Aug. 13, 2015. Credit: Hal Yeager
Perseid meteors seen over Allgood, Alabama on Aug. 13, 2015. Credit: Hal Yeager

Comet Swift-Tuttle has a very eccentric– oblong – orbit that takes this comet outside the orbit of Pluto when farthest from the sun, and inside the Earth’s orbit when closest to the sun. It orbits the sun in a period of about 133 years. Every time this comet passes through the inner solar system, the sun warms and softens up the ices in the comet, causing it to release fresh comet material into its orbital stream. Comet Swift-Tuttle last reachedperihelion – closest point to the sun – in December 1992 and will do so next in July 2126.

Although the Perseid meteor shower gives us one of the more reliable productions of the year, the ins and outs of any meteor shower cannot be known with absolute certainty. Forecasting the time and intensity of any meteor shower’s peak – or multiple peaks – is akin to predicting the outcome of a sporting event. There’s always the element of surprise and uncertainty. Depending on the year, the shower can exceed, or fall shy, of expectation.


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