Perseid meteors set to put on a show
2012 Perseid meteor shower will peak overnight Aug. 11-12
One of the most dazzling shows of the year is upon us, but you won't need a ticket to see it live. A front-row view may be as close as the nearest open space or rooftop.
The annual Perseid meteor shower takes centre stage this weekend, painting the night sky with glowing streaks of light. The spectacle begins every year in mid-July and lasts through August, but the best time to take in the show this year is when the meteor shower peaks on Saturday night and early Sunday.
The show is free, so grab a blanket and head outside to watch the spectacle. And if you miss the event this year you can always catch it again next August. This performance has a standing engagement.
What's the best place to watch meteor showers?
Find the darkest place you can, with an open sky and away from light pollution. Try to get outside any settled area. If there is a bright moon, try to position yourself so its light is shielded from your field of vision.
Unlike last August, when the glare of the full moon made it hard to see some of the more modest meteors, this year the waning crescent moon "should be considered more of a nuisance than a deterrent," the International Meteor Organization says.
The Perseids are best observed in the mid-northern latitudes, while in the southern hemisphere they "cannot be usefully observed," according to the IMO.
Meteors can appear anywhere in the night sky and they are safe to watch with the naked eye. In fact, that's a better way to watch than with binoculars or a telescope, which restrict the field of view.
To check for clear skies in your area, one way is with the Clear Sky Charts website, which forecasts astronomical observing conditions in North America.
In southern Ontario, the Torrance Barrens Dark-Sky Preserve is an excellent location to watch for meteors, because of the absence of light pollution.
Annual major meteor showers
Visible each year in early January, this meteor shower appears to originate within the constellation Bootes. The meteors are often bright blue, and peak at an hourly rate of about 40.
This shower begins every year in mid-April. The Lyrids can sometimes produce fireballs with smoky trails that can linger for a few minutes. They appear to come from the star Vega, in the Lyra constellation.
Debris left behind from the 109P/Swift-Tuttle comet, which passes through the inner solar system every 130 years, is responsible for the Perseid meteor showers. The event begins in mid-July, but peaks in mid-August.
Known to produce fireballs, these meteor showers will peak in late October with a maximum hourly rate of about 20. The yellow and green meteors are fast-moving and come from fragments left behind by Halley's comet.
The Leonids are visible every year around mid-November when Earth passes through the debris field left by comet 55P/Tempel-Tuttle. Leonids hit the Earth's atmosphere at 70 kilometres per second, or 255,600 km/h. That's about 133 times faster than an F-18 fighter jet can fly at top speed.
The Geminids are known for their multi-coloured streaks and moderate speeds — they travel at half the speed of the Leonids — making them easy to spot. The shower peaks in mid-December, with an average maximum rate of 50 meteors an hour.
When is best to view the Perseids?
The best viewing nights are August 10 to 16, when the moon won't be seen. The best night to view the Perseids this year is Saturday to early Sunday (Aug. 11-12).
The best time is from 10:00 or 11:00 p.m. local time, onwards.
Where will the Perseids be in the sky?
The Perseids appear to originate from a point within the constellation Perseus.
Look northeast. Perseus will be low in the sky early at night and rise higher in the sky through the night. The constellation has an inverted Y shape.
The meteors won't appear evenly spread out through the night, as they come in waves. With a clear sky and from a dark site, observers should be able to see about 100 per hour at the peak. Visibility improves as Perseus gains altitude.
A week before or after the peak, the meteor shower should still be at about 20 per hour.
The meteors will appear as long, thin bright stripes across the sky, most lasting just a fraction of a second.
The speed of meteors makes photography challenging. One approach is to put a camera on a tripod or steady surface to keep it absolutely still, and take a series of photos with long exposure times (up to several minutes) — if you're patient, there's a good chance you'll catch the streak of a meteor.
Lower-end cameras may not have a long-exposure feature, but many DSLR cameras have settings that will at least let you manually do a very long exposure by either holding down the shutter button itself or attaching a shutter cable that allows you to do the same thing with less risk of moving the camera.
What's the best way to watch them?
Lying down will work better than standing up, so take a blanket.
The darker the sky, the easier it is to spot meteors. It takes about 20 minutes for the the human eye to adapt to the dark, so be patient at first.
So avoid looking at any articifical light while watching for meteors. If you'll need a light to find your way or check a constellation map, many stores carry flashlights and headlamps with red bulbs or filters that have less impact on the eye's night vision than a bright white light.
What's a meteor shower?
Meteor showers occur when the Earth encounters the debris fields left behind by visiting comets. As comets travel through space and near the sun, small particles of rock and metal break off, leaving fragments in their wake like a trail of crumbs.
For example, the Perseids streak through the sky when the Earth is passing through debris from Comet Swift-Tuttle. Comet crumbs called meteoroids hit the top of Earth's atmosphere at hundreds of thousands of kilometres per hour, burning up because of friction. This may make them glow for several seconds, lighting up the night sky.
If a part of the meteor survives the trip through the atmosphere and hits the ground, it's a meteorite. But that is a rare occurrence.
Meteoroids are usually pretty small. According to NASA, most meteors range in size from one millimetre to one centimetre in diameter, barely more than a grain of sand. The light they produce while burning up, however, is very intense and can be seen from hundreds of kilometres away.
Many people still call these celestial fireworks "shooting stars," even though they don't have anything to do with stars.
Why are they so bright?
The intense light results when "a meteoroid compresses the air in front of it like water before a speedboat, creating a white-hot shock wave," says Stephen Craft of Sky and Telescope. "This is what you mostly see — not the little bit of debris itself."
The colour of light produced depends upon the composition of the meteorite. Iron particles produce yellow light; sodium particles produce orange-yellow light; magnesium produces a blue-green light and silicon atoms produce red light.
How are they named?
The debris from a comet travels in parallel lines, and when that hits the Earth's atmosphere, it appears to originate from a single point, just as parallel train tracks appear to converge to a single point in the distance.
The Perseids, for example, get their name from the constellation Perseus, because that is where the shower appears to originate. Similarly, November's Leonids appear to come from within the constellation Leo and December's Geminids appear to originate from within the constellation Gemini.