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Astro Bob: Pursuing the Perseids

The annual Perseid meteor shower radiates from a point in the constellation Perseus just below the W of Cassiopeia. Rates are usually about 100-120 meteors per hour from a dark, moonless sky at peak but will be cut in half due to moonlight this time around. This map shows the sky facing east around midnight Aug. 12-13. (Source: Stellarium)1 / 4
A brilliant Perseid meteor called a fireball. (Credit: NASA)2 / 4
Composite of bright Perseid meteors recorded by NASA all-sky cameras in 2011. Each is a grain rock shed from the tail of comet 109P/ Swift-Tuttle. Every year in mid-August, Earth passes through the comet’s debris trail as it orbits around the sun. Any particles we smack into burn up as meteors about 60-70 miles overhead. (Credit: NASA)3 / 4
Bob King4 / 4

Get ready for the darling of meteor showers this week — the Perseids. Who can deny their appeal? Not only is the shower rich with fiery flashes of meteoric light, but it happens in August when the weather’s nice. Peak activity is expected Tuesday night, Aug. 12-13. when up to 100 meteors an hour might be seen.

Ah, but there’s a rub. This year the moon will be nearly full and drown out the fainter shower members. Instead, we’re more likely to see something like 30 meteors an hour. That’s still respectable enough to risk losing a little sleep for the sake of heavenly fire.

Find a place away from glaring lights to allow your eyes to adapt to the darkness. That way you’ll see more meteors. While the Perseids spit out the occasional fireball, most shower members are going to be closer in brightness to the stars of the Big Dipper. Some leave “smoke” trails called meteor trains. They’re actually tubes of glowing air molecules created as the meteoroid particles speed through the atmosphere at 130,000 mph. Though they might look close, most meteors burn up 60-70 miles overhead.

Perseid meteors radiate from the constellation Perseus (hence the name) located a short distance below the “W” of Cassiopeia in the northeastern sky. To know for sure if you’ve seen the genuine item and not a random meteor, follow the trail backward — if it points toward the northeast, you’ve got a ringer!

You can start watching Tuesday night. The later you stay up, the more meteors you’ll spot because the radiant or point in the sky from which the meteors appear to radiate rises higher with every hour. To view the shower, all you need are your eyes and a comfortable chair. OK, it’s nice to have a friend along, too, for conversation and to keep you from falling asleep. Set up facing to the east or southeast with Perseus off to your left. Sit back, look up and enjoy.

The Perseids are the left-behind sand, seed and pebble-sized particles from comet 109P/Swift-Tuttle. Discovered in 1862, it circles the sun every 120 years. Over millennia, the comet has left a stream of debris along its orbit, which the Earth passes through every year in mid-August. Comet grit hits our atmosphere like bugs smacking a car’s windshield and vaporizes in a flash of light we call a meteor or shooting star

While shower maximum occurs on Wednesday morning, you’ll still see a scattering of meteors tonight through the end of the week, so don’t pass on the event if the weather doesn’t cooperate Tuesday. Good luck!

Bob King is the News Tribune’s photo editor and an amateur astronomer. Read more on his blog at