Every August, just when many people go vacationing in the country where skies are dark, the best-known meteor shower, makes its appearance.
This year, the Perseid meteor shower is expected to reach its peak overnight on Monday (Aug. 12), and there are some key tips to keep in mind for your “shooting stars” viewing.
Peak activity for the Perseids is unfortunately predicted for the daylight hours across North America, so stargazers with clear skies are encouraged to seek out the meteor display during the pre-dawn hours of Monday and again during the early morning hours of Tuesday (Aug. 13). At these times, the absence of bright moonlight can maximize your chances of spotting a meteor.
At mid-northern latitudes, moonset on Sunday evening (Aug. 11) occurs at about 10:15 p.m. local time and around 10:50 p.m. the following night. Since dawn doesn’t break until around 4:30 a.m. local time that means there will be between five-and a-half to six hours of dark, moonless skies for the two best viewing nights for the Perseids.
Every year during mid-August, the Earth passes near the orbit of Swift-Tuttle and crosses the comet’s debris stream. The comet material left behind then ram’s into our atmosphere at approximately 37 miles per second (about 133,000 mph/214,000 km/h) to create bright streaks of light in our mid-summer night skies.
Comet Swift-Tuttle made its most recent appearance more than 20 years ago, in December 1992. Its orbit is highly elongated and as such it takes roughly 130 years to make one trip around the sun.
For several years before and after its 1992 return, the Perseids were a far more prolific shower, appearing to produce brief outbursts of as many as several hundred meteors per hour, many of which were dazzlingly bright and spectacular. The most likely reason was that the Perseids parent comet was itself passing through the inner solar system and that the streams of Perseid meteoroids in the comet’s vicinity were larger and more thickly clumped together, leading to brighter meteors as well as much-higher-than-normal meteor rates.
But now, with the comet now having retreated nearly 3.2 billion miles (5.1 billion km) back out into space, Perseid activity has returned to normal.
Perseid meteor clumps
A very good meteor shower will produce about one meteor per minute for a given observer under a dark country sky. However, any light pollution from city lights or moonlight considerably reduces the count.
The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity nominally yield 90 or 100 meteors per hour. However, observers with exceptional skies often record even larger numbers.