Every year, the month of August brings with it a summer-night classic: the Perseid meteor shower. From August 10 to 14, lovers of the starry sky will get to observe dozens of meteors an hour.
Shooting stars in fact are specks of dust, the size of a grain of sand, that enter the Earth’s atmosphere at terrific speed, around 201,000 kilometers an hour for the Perseids. At that velocity, the bit of dust covers a great distance before being completely consumed and leaving in its wake the long luminous tail characteristic of shooting stars.
The role of comets
It is comets that are responsible for shooting star showers. As they circle the Sun, comets, which are made up of ice and rock, leave behind them a cloud of dust. Many of those clouds cross the orbit of the Earth. When our planet passes through one of those clouds, a large number of dust particles penetrate the Earth’s atmosphere.
The Perseid shower is due to Comet Swift-Tuttle, discovered in 1862 by astronomers Lewis Swift and Horace Tuttle. It orbits the Sun in 133 years ‒ its last passage going back to 1992 ‒ resupplying the dust cloud that generates the Perseids.
Why the Perseids?
When they’re seen from the ground, an observer will have the impression that the meteors in a shower hail from a given area in the sky, which we call the radiant. The name given to the shower is the name of the constellation in which the radiant is located. The constellation Perseus is home to the radiant of the shower for the month of August, whence the name Perseids.
There are several dozen meteor showers, but the Perseids is one of the three strongest. In ideal conditions (a perfectly clear sky with no light pollution), it’s estimated that we can observe up to a hundred or so meteors per hour at the maximum of the shower. The Perseids’ popularity stems from the fact that it takes place during the summer season.
The Earth will be passing through the cloud left behind by Comet Swift-Tuttle between July 17 and August 24, but between August 10 and 14 the show will be more spectacular. The maximum intensity will happen this year on August 12 between 4 a.m. and 5 p.m.
The Moon will be coming to spoil the show
The Perseids’ radiant appears above the northeast horizon in the early evening and continues to rise until dawn. The second part of the night is therefore the best time for observing the meteors.
Unfortunately, this year the Moon will be in the last quarter on August 11, which will hinder observations considerably during the favorable late-night period. You’ll have to take advantage of the period between ten o’clock at night and one o’clock in the morning to observe these cosmic specks of dust.
To fully enjoy the phenomenon, I advise you to stretch out on a chaise longue with a blanket, because the nighttime in August can be cool. Lie down facing east, then let your eyes wander over the starry sky. Get out your wish list, because you’re certainly going to see shooting stars. And even though your wishes probably won’t come true, you’ll still enjoy a magnificent celestial spectacle.