Prime viewing awaits observers of this year’s Perseid meteor shower
A moonless sky and (hopefully) cloudless nights promise exceptional viewing of this year’s most popular meteor shower — the Perseids.
The best time to observe is between midnight and dawn on the mornings of Aug. 12 and 13. Under dark skies, 60 or more meteors are typically seen each hour. The darker the sky, the more meteors you’ll track.
If you’re unable to stay up late on those days, try Saturday night. An enjoyable number of meteors will be visible — and you can sleep late the next morning.
Watching the Perseid meteor shower is popular because it assures spotting an abundance of meteors, some of which are dazzling fireballs, streaking across your favorite night skies.
During exceptional years, I’ve counted more than 300 meteors during a single night. However, just like people, each year’s meteor shower exhibits its own personality.
Perseids radiate from and are named after an upside down “V” shaped constellation called Perseus. During August, this loose nest of stars rises above the northeast horizon before midnight. More meteors are visible the higher this radiant rises.
Perseid meteors flame across the sky as the Earth passes through vast ribbons (streams) of scattered sand and small rock-size debris once shed by Comet Swift-Tuttle as it orbits through the solar system every 133 years. This comet was discovered by American astronomers Lewis Swift and Horace Tuttle back in the Civil War days of 1862.
Each time Swift-Tuttle passes through the warmth of the inner solar system, its frozen, 16-mile-wide nucleus releases debris along the comet’s path — through which the Earth passes each summer.
As this debris slams into the Earth’s thin upper atmosphere, it rapidly slows down and then disintegrates in a luminous streak of light we popularly call a shooting star.
Perseids swiftly move across the sky at a speed of nearly 40 miles per second.
Though some meteors — especially bright ones — appear rather close, most burn up in the atmosphere at a height of about 60 miles. Meteors seen along the horizon are a few hundred miles distant.
If you’re counting meteors, notice there are times when numerous meteors are visible followed by a near absence of activity. Tracking such meteor clusters and gaps helps astronomers better understand the scattering of space debris released by comets such as Swift-Tuttle.
From years of observing, I’ve seen Perseids streak across the sky as early as the first week of July to as late as the final week of August. This nearly two-month spread suggests that comet debris has spread widely since Swift-Tuttle first passed though the inner solar system thousands of years ago.
On the other hand, if Perseid meteors were only visible for a few days or hours each year, this would suggest Comet Swift-Tuttle is a young visitor to the inner solar system because its debris has yet to spread much outside the comet’s original path.
I’m often asked what part of the sky is best to watch. It depends.
Since the Perseids radiate from the northeast, you will generally see more meteors with shorter tails when watching the northern sky. Fewer but longer-tailed meteors are commonly seen skipping across the Earth’s atmosphere when looking toward the southern sky.
If you live in the glare of city lights, try watching the darkest portion of the sky from your backyard, a nearby park or school grounds. Some of the best local dark skies are found in the Horse Heaven Hills and foothills of the Blue Mountains.
Plan on spending a few hours outside? Take a comfortable folding chair, keep a warm blanket nearby, and bring snacks. And remember to let your eyes adapt to nighttime darkness. This will greatly increase the number of meteors seen.
Watching meteors is a fun way to introduce friends and family to the enjoyment of the heavens. Your children will never forget resting atop sleeping bags and spotting bright meteors changing shape and color as they speed across the summer’s Milky Way.
This story was originally published August 8, 2018 at 5:42 PM.