Eyes up for the annual Perseid meteor shower


This year could be an 'outburst' year with twice the number of sightings as usual.


A time-lapse image of a Perseid meteor outburst in August 2009.
NASA/JPL

The Perseid meteor shower will peak this week, with the most activity between 11 and 12 August.

The shower, which occurs as Earth passes through the trail left by the Swift-Tuttle comet, is expected to be especially vivid this year. Astronomers say the conditions are right for an “outburst”, with the potential for more than double the usual 80 sightings an hour – at least in the Northern hemisphere.

“Under perfect conditions, rates could soar to 200 meteors per hour,” NASA meteor expert Bill Cooke says.

The meteors light up when specks of material from the comet hit Earth’s atmosphere (or when the Earth’s atmosphere hits it). This shower is called the Perseids because they seem to fly out of the constellation Perseus.

Usually Earth just slides past the edge of the comet’s debris stream but this year, with Jupiter’s gravity pulling the dust closer to us, Earth will pass through the middle of the trail. Astronomers believe this year could be one of those events.

Earth began passing through the cloud of dust on 17 July and will have cleared it by 24 August, but the shower's peak — when Earth passes through the densest, dustiest area — will be between midnight and dawn on the morning of 12 August.

In the Northern Hemisphere, a few Perseids will be visible in the early evening and, while they might not be so plentiful, this is the best time to try to see an “earthgrazer" – a long-lasting meteor travelling horizontally across the sky.

In the Southern Hemisphere, the Preseids are visible from tropical and sub-tropical zones, but not until well after midnight.

Comet Swift-Tuttle is the largest object to regularly swing by Earth, last passing us on its orbit around the sun in 1992. It’s next run will be in 2126.



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