For many avid skywatchers and outdoor enthusiasts, August is synonymous with shooting stars. The 2020 display of the famous Perseid meteor shower, in full swing by mid-month, won’t take place under optimal conditions. But have no fear, because the planets will steal the show during these wonderful summer nights!
Moon versus Perseids
Meteors, or shooting stars, are the brief streaks of light produced when tiny dust particles plunge into the Earth’s atmosphere at several dozen kilometres per second. The kinetic energy of the space debris is converted into heat and light due to friction with the air molecules. Every now and then, the Earth in its orbit passes through dense streams of dust left behind by comets that break up as they repeatedly swing by the Sun. The result is a meteor shower. And since the Earth returns to the same point in its orbit around the same dates every year, these showers recur periodically. For example, the famous Perseids show up annually in mid-August when the Earth crosses the debris-littered orbital path of comet Swift-Tuttle.
The quality of the annual celestial performance depends on a variety of factors. Most are inherent to the particle stream itself: the abundance, density, and average size of its dust particles, its position relative to the Earth’s orbit, the number of years since the parent comet’s last passage, etc. There are also a few external factors at play, some of which are unpredictable in the long term, like the weather, while others can be determined well in advance. Perhaps the biggest factor is the Moon’s phase, which makes it easy to determine whether moonlight will interfere with viewing on the shower’s peak nights. In essence, it’s a competition between the lunar glare in the sky and the faint streaks of light from the dimmest meteors: Only the brightest (which are fewer in number) will be able to pierce that luminous veil.
This year, the Perseids will reach their peak on August 12, somewhere between 4 a.m. and 5 p.m., which is daytime for Quebec observers. The best viewing should come the night of August 11-12, since it’s closest to that theoretical peak. But the last quarter Moon on August 11 can’t be overlooked, so we’ll have to settle for a short window of dark sky that occurs after the end of astronomical twilight and before moonrise, i.e., between 10 p.m. and 1 a.m. Unfortunately, this will compromise the Perseids’ prime viewing hours, which are just before dawn. We can nonetheless expect to see about thirty meteors per hour under dark skies far from urban light pollution; that number drops by half in suburban areas.
Although the number of meteors diminishes rapidly when observing farther from the night of peak activity, you’ll probably get a chance to spot a few shooting stars between late July and the third week of August, when the Perseids are still mildly active.
Jupiter and Saturn at their best
If the Moon, the weather, or light pollution ruin your plans to check out the Perseids, the planets will give you lots to see throughout August. The first to make an evening appearance are Jupiter and Saturn: This remarkable duo can be spotted above the southeastern horizon at nightfall and culminate due south at about 10:30 p.m. by mid-month. The two gas giants are currently hanging in the eastern part of the constellation Sagittarius, to the left of the Teapot asterism. On the evening of August 1, the waxing gibbous Moon lies below Jupiter and forms a triangle with Saturn. This scene repeats itself on the night of August 28-29 when the Moon returns to the same section of sky.
Jupiter, the brighter of the pair, is on the right. Any small telescope will allow you to clearly make out its four largest moons, which change configuration every evening. You’ll also glimpse some of its cloud bands, which vary in size and run parallel to the planet’s equator. A higher-quality instrument and stable viewing conditions will reveal finer details, such as the swirls and festoons along the borders of each band.
Through a telescope, Saturn’s atmosphere appears much blander than that of its neighbour. But those famous rings are what really capture our attention, and they’re nothing short of spectacular! This year, the rings are tilted about 22 degrees toward Earth, giving observers with good-sized telescopes the opportunity to examine the main structures. Saturn’s largest moon Titan can also be spotted using small amateur instruments: It appears as a tiny star that tags along with Saturn on its journey through space.
Mars heads toward opposition
Once Jupiter and Saturn culminate in the south, another planet emerges above the eastern horizon. You’ll have no trouble identifying the famous Red Planet, given its orange hue and the fact that it’s the only really bright object in the constellation Pisces. Through a telescope, Mars’s diameter currently exceeds 15 arc seconds, so it’s time to turn your gaze upwards: Train your eye to spot the lighter and darker areas of the Martian surface visible with a telescope. But before you point your instrument at Mars, wait for it to rise high enough above the horizon, sometime around 1 a.m. in mid-August. Observation conditions will continue to improve over the next few weeks as the planet peaks earlier and earlier, until it reaches opposition in October. For several weeks between September and November, the Red Planet will show itself to us better than it has in 15 years, so get ready for this rare opportunity to explore its most subtle details. On the night of August 8-9, the waning gibbous Moon moves to within only 1 degree below the Red Planet: a spectacular view!
Venus and Mercury at dawn
Another planet emerges above the east-northeastern horizon after 2:30 a.m.: brilliant Venus, which reaches its greatest elongation on August 12, 46 degrees west (i.e., to the right) of the Sun. At dawn, about thirty minutes before sunrise, the Morning Star twinkles majestically about thirty degrees above the eastern horizon. Then, on the morning of August 15, the waning Moon hangs a mere 3½ degrees above Venus.
The last planet to rise is Mercury, which, in the first week of August, ends its very good morning apparition that started in July. The tiny planet can be spotted 30 minutes before sunrise, low on the east-northeastern horizon: Mercury is relatively bright at the moment, but binoculars will help you find this little dot of light in the glow of approaching sunrise.