Science

The Perseid meteor shower is underway: How and when to catch a 'shooting star'

If you have clear skies — and hopefully smoke-free — step outside and look up over the coming days and you will likely see a few meteors streaking across the sky.

Keep an eye on the sky in the days ahead — and even after next week's peak night

The Perseid meteor shower is considered the best of the year, thanks to often-favourable weather and the roughly 100 meteors an hour it produces at its peak. (Submitted by Alan Dyer/AmazingSky.com)

If you have clear — and hopefully smoke-free — skies, step outside and look up over the coming days and you will likely see a few meteors streaking across the sky.

The Perseid meteor shower has begun, with its peak coming next week.

The shower is considered the best of the year for two reasons: It occurs at a time with more favourable weather (that being clear skies and warm nights) and it produces roughly 100 meteors an hour at its peak. It is only second to the Geminids, which produces roughly 120 meteors per hour, but falls in December, when it's often cloudy.

Meteors are small particles of dust or debris from space — some as small as a grain of sand — that burn up in Earth's atmosphere.

On any night of the year, if the sky is clear, you can always catch a meteor or two streaking across the sky. But roughly once a month, we get a particularly active meteor shower as Earth passes through a stream of debris left over from a comet or asteroid.

In the case of the Perseids, Earth is moving through debris left over from Comet 109P/Swift-Tuttle.

Comets — often referred to as "dirty snowballs" — are a collection of ice and debris, as well as elements like carbon dioxide, carbon monoxide and water that are trapped beneath its surface. Like the planets, comets orbit the sun, but most often much farther out than the planets. As they near the sun, those elements sublimate — or go from a solid into a gas, forming that tail associated with comets.

Try out this interactive map showing how Earth passes through a meteor shower:

But comets also release dust particles. Smaller, micrometre-sized particles are blown away by solar radiation, leaving behind some of the larger ones. These then interact with other planets, such as Jupiter, which affects how the debris is spread out in its orbital path.

This is why in some years, there are outbursts of activity, with more meteors seen per hour than normal.

The Perseid meteor shower runs from around July 17 to Aug. 24, peaking across Canada this year on the night of Aug. 11-12, according to the International Meteor Organization. (Though some sources pin the peak on the night of Aug. 12–13.)

Understanding 'outbursts'

Comet 109P/Swift-Tuttle makes several visits close to the sun, so there's a "very complex structure" that's following it, explained Denis Vida, a meteor physics postdoctoral associate at Western University.

"You can think of it as like a jester's hat, with all the little dangling bits on either side. So it really depends year to year which part Earth is going to go through," said Vida.

"That's why we see certain enhancements of activity in a particular year, where some other years, we've kind of just passed through the bulk area of the shower, which doesn't have any enhanced activity."

So will this be an outburst year? Unfortunately not. The next outburst is expected in 2027 and 2028, Vida said.

The Perseids also show no sign of slowing down, he said, despite a recent article suggesting that the annual shower was weakening.

"We can't really say that there's a significant change over the years, but we can definitely see that we have some outburst in particular years," said Vida, noting there was a big outburst in 1993 and another in 2016.

Still, the Perseids rarely disappoint. Even in cities, with plenty of light pollution, you can expect to see several meteors an hour, many producing long, bright trails of light or even fireballs.

How and when to watch

Watching a meteor shower is a great activity for the family; you don't need binoculars or a telescope — just your own two eyes. And the great part is that the moon will only be roughly 13 per cent illuminating during next week's peak, meaning it won't wash out faint meteors the way a full moon would.

The best thing to do is to get to as dark a location as possible, which will increase your chances of seeing faint meteors. But keep in mind that meteors are fleeting, with most lasting less than a second. If you take your eyes off the sky, you may miss one. 

And while the meteors will appear to be coming out of a particular part of the sky, toward the constellation of Perseus (hence, the shower's name), all you have to do is look up.

The area of the sky from which the Perseids seem to originate, called the radiant, is seen here. (American Meteor Society)

You'll also want to put away your cellphone or any other source of light; you want your eyes to adapt to the dark, which can take as long as an hour.

Try to lie down and get comfortable. If you're just standing with your neck craned, you'll likely get tired. But mostly remember to be patient: Standing outside for just a few minutes won't cut it. Give yourself an hour or more.

Your chance of viewing meteors also increases the later you stay up, as many more are typically seen around 4 a.m.

If you don't have clear skies next Wednesday, the night of the peak, don't fret: the shower will continue to be quite active until roughly Friday.

Want to participate?

Western University is well known for its meteor physics study, with all-sky cameras that monitor the sky for fireballs and meteor activity, in order to better understand meteors and potential outbursts.

Vida leads the university's most recent endeavour, the Global Meteor Network, a collection of 500 wide-field sky cameras with increased sensitivity that are set up across the globe.

It's something in which anyone can participate, including during the Perseids.

"We designed blueprints and wrote instructions on how to build these cameras, how to properly calibrate them and how to send the data back to our servers — and we did it in such a way that anyone can build a camera with a little bit of money and a lot of goodwill," Vida said. 

If you're not a do-it-yourselfer, you can also purchase a camera, he said. It's a great way to participate in some citizen science and discover just how many meteors you may be missing out on from night to night.

But for now, remember to keep an eye on the sky: meteor activity will increase over the coming days as we head toward the peak.

ABOUT THE AUTHOR

Nicole Mortillaro

Senior Reporter, Science

Nicole has an avid interest in all things science. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books.

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