Perseid meteors streak across the sky early Aug. 12, 2008, near Rogers Spring in the Lake Mead National Recreation Area, Nevada.Ethan Miller
One of the year's brightest shows is on Thursday night - and best of all, it's free.
The Perseid meteor shower, one of the most spectacular of the year, will be visible all night, as debris from the tail of Comet Swift-Tuttle falls into the earth's atmosphere.
The meteors are centered on a spot near the Perseus constellation. In the early evening, it will sit low in the northeastern sky. As the night progresses, it will move steadily upward.
The most spectacular point of the shower will happen about 3 or 4 a.m., in the hours before first light.
At the shower's peak, as many as 100 meteors per hour will streak across the sky. Light pollution, however, could mean that far fewer of these objects will be visible to city-dwellers. It will, however, be more visible than last year, as the moon will be smaller.
Ray Jayawardhana, an associate professor at the University of Toronto's Department of Astronomy and Astrophysics, said those hoping to see the shower should seek out a dark place.
"I certainly think from the outskirts of the city or perhaps from the roof of a building," he said.
Ralph Chou of the Royal Astronomical Society, said there have been reports of extremely large meteors in this year's Perseid, including one, spotted in Hungary, that was about 10 times the brightness of Venus.
"It looks like we are going into more dense pieces of meteoric debris," he said. To put it in context, most of the meteors are only about the size of a pea, with a particularly bright one perhaps the size of a ping-pong ball or a computer mouse, he said.
If the skies are clear enough for good viewing, the David Dunlap Observatory in Richmond Hill will hold an open house from 9:30 p.m. ET to midnight. Participants are encouraged to bring a blanket or a lawn chair to lie back and watch the sky. Members of the Royal Astronomical Society will have telescopes set up and will be on hand to answer questions.
The observatory will post a notice on its website around 6 p.m. indicating if the weather will be clear enough for good viewing.
About 300 people came out to the open house during last year's Perseid Shower. About 1,000 people flocked to the observatory earlier this month for a rare southerly glimpse of Aurora Borealis.
The show will be visible everywhere on Earth, but more visible in the northern hemisphere than the south.
The Toronto forecast for tonight predicts mostly clear skies with a few clouds. Vancouver will be clear. The forecast for Calgary, Edmonton and Winnipeg is cloudy with thunderstorms. Ottawa should be mostly clear. Forecasts for Quebec and the Maritimes call for a mix of clear skies and cloudy periods.
Adrian Morrow