The summer's best shooting star show is expected be even more spectacular this year, thanks to an unusual "outburst" that only happens about once a decade.
Astronomers predict the Perseid meteor shower, which peaks on the night of Aug. 11-12, will produce about double the number of meteors as it normally does.
The Perseids happen each August as Earth passes through the stream of dust and debris left by the comet Swift-Tuttle. As those particles or meteoroids smash into the Earth's atmosphere and burn up, they produce bright streaks across the sky that we see as meteors or shooting stars.
During a typical year, if skies are dark and clear, you can expect to see a meteor every minute to every 30 seconds during the peak, says Peter Brown, a professor with the Meteor Physics Group at Western University in London, Ont. "And a lot of those meteors will be pretty bright."
This year, he says, "the rates could be up to … a couple every minute, maybe even three a minute" if you're camping or at the cottage, away from city lights. Dark skies are key to seeing lots of meteors."
In Canada, no matter what province you're in, the best time for viewing is between midnight and sunrise on Aug. 12, with improving views after the moon has set and the constellation Perseus — where the meteors will appear to originate — gets high in the sky.
That's technically a few hours after the official peak of the meteor shower, but Brown says, "It's far more important to be out when the moon is down in terms of the numbers you'll see than whether you're within an hour or two or four hours of the peak."
That said, the Perseids produce lots of brighter meteors that are visible even when the sky is not completely dark.
It's also worthwhile looking for them even at 10 p.m. (during the official peak), just after sunset, when Perseus is low in the sky and the meteors are entering the atmosphere at a shallow angle.
Such "grazing" meteors are "very spectacular," Brown says. "They may last multiple seconds. And you'll see them scoot over a good portion of the sky."
Perseids are also expected to be visible for a couple of nights after the peak (so don't despair if it rains on Aug. 11) and all week before the peak, and skies will be darker then, as the moon is new on Aug. 2.
"You won't see one meteor a minute, but you may see one meteor every two minutes," Brown suggests.
Risk for satellites
This year's outburst is caused by the influence of Jupiter's and Saturn's orbits on the Swift-Tuttle debris, Brown says.
The last such outburst happened in 2009, when the Perseids produced about double the number of meteors.
But a series of outbursts in 1992, 1993 and 1994 generated even more spectacular shows.
"There, the activity was five or six times normal," Brown says.
Even though Perseid meteors are very small — dust particle-sized to a few millimetres in diameter — they can cause damage to satellites, particularly during outbursts.
A European Space Agency telecommunications satellite called Olympus was permanently disabled by a Perseid in 1993 and the Landsat 5 satellite managed by NASA and the U.S. Geological Survey temporarily spun out of control after being hit by a Perseid in 2009.
Despite their minuscule size, the space particles create a lot of free charge and plasma when they hit a satellite, which can interfere with electronics, Brown says.
This year, he adds, "we're paying particular attention because this enhanced Perseid activity may also be correlated with some impact probabilities or increased impact danger to satellites."
In the meantime, the peak of the Delta Aquarids meteor shower was officially the night of July 28-29. That show doesn't produce as many meteors as the Perseids, and they're better seen from the southern hemisphere. But between the end of the Delta Aquarids and the start of the Perseids, it's worthwhile to start keeping your eye out for meteors this week.