It’s peak season for shooting stars now that August is here and the nights are getting longer. The famous Perseid meteor shower, which is in full swing by midmonth, is occurring this year under almost ideal conditions.
The solar system isn’t exactly a “tidy” place. As it orbits the Sun, Earth constantly collides with interplanetary dust and small stones. These particles plunge into Earth’s atmosphere at speeds of tens of kilometres a second. They heat up very rapidly and produce a fleeting trail of light, which we call a meteor or, more poetically, a shooting star.
Earth sometimes ploughs through clouds of dust strewn across its orbit (the debris is usually from comets leaving solid particles in their wake as they repeatedly pass by the Sun). These encounters trigger the famous meteor showers that occur the same time every year. During a meteor shower, the effect of perspective gives the impression that the meteors are emerging from a well-defined area of the sky. The constellation where this “radiant point” is located gives the shower its name.
Ideal conditions for the Perseids
Campers and outdoor enthusiasts are very familiar with the Perseids, a gift from Comet Swift-Tuttle. The Perseids are among the three most spectacular meteor showers of the year and the only one occurring in summer. Viewing conditions vary, however, from year to year, mainly on account of the lunar phase. This year during the Perseids, there will be a New Moon, which creates stellar conditions for seeing shooting stars.
This year’s show also benefits from another key factor: Earth will cross the densest part of the cloud of dust just before dawn in Quebec. As a result, we should have a ringside seat for the most intense part of the shower.
To admire the display of shooting stars, try watching from the darkest spot you can find. At peak time (from 2:30 to 5 a.m. the night of August 12 to 13), you’ll see up to 70 meteors an hour, provided the sky is clear and totally free of light pollution. If the sky is just moderately dark, only half as many meteors will be visible.
To avoid light pollution, you might need to travel dozens or even hundreds of kilometres away from a big city. But even if you stay in the city, you can still spot a few of the brightest meteors from a fairly dark backyard. Avoid standing near streetlamps, though. And ask your neighbours to turn off their porch lights.
If the weather doesn’t cooperate, remember that the Perseids play out over several days. The shower’s intensity, however, drops by half for each day before or after the peak.
What about the planets?
For now, Saturn is the only planet visible in the evening. Look for it in Libra, near the head of Scorpius. It’s just under 20 degrees high in the southwest at nightfall, which is the best time to observe the amazing ringed planet before it sinks too low on the horizon. On August 22, Saturn can be seen alongside the first quarter of the Moon.
For most of August, Venus isn’t visible because it’s too close to the Sun. On August 15, it passes between Earth and the Sun (inferior conjunction). The planet reappears, however, in the dawn sky during the last mornings of the month. Look for the Morning Star a few degrees above the east horizon 45 minutes before sunrise. Mars, which is much dimmer, is also visible about 10 degrees higher and to the left.
Note, too, that the Full Moon on August 29 will occur less than 24 hours after lunar perigee (the moment when our satellite is closest to Earth). The moonrise, which will be opposite the setting sun in the sky, promises to be dazzling. But above all, this coincidence will have an observable effect on the tides. From August 31 to September 3, the tidal range will be especially large, among the largest of the year. The tidal range during the Full Moon in September will be even greater.