A blue moon, two giant planets and a meteor shower: August has no shortage of astronomical events this year! So grab a blanket and a hot beverage, and we’ll run through everything you need to know about the August sky.
Let’s start by setting the record straight: No, the Moon won’t be turning blue anytime soon. The term “blue moon” refers to the second full Moon in a calendar month. In this case, it’s referring to the full Moon on August 31st, which follows the first one on August 1st. Since the lunar phase cycle lasts about 29.5 days, it should come as no surprise that two identical phases (new, full, quarter) can occur at the beginning and end of a 31-day month. Admittedly less impressive than seeing an actual blue Moon, this is still a relatively rare event that happens only every two or three years. It’s also where the expression “once in a blue moon” comes from.
As coincidence would have it, the two full Moons of August 2023 are also known as “perigee” moons, since they occur within just a few hours of the time our natural satellite comes closest to Earth in its orbit. The Moon’s angular diameter in the sky is then slightly larger than average—but this is not directly visible to the naked eye. The full Moon on August 31 will be the biggest of the year, as it occurs less than 10 hours after the Moon’s perigee. The August 1st full Moon is the second largest of 2023.
The giants and their escorts
The August nights will also be an ideal time to observe the two gas giants: Jupiter and Saturn.
The largest planet in the solar system and fourth-brightest object in the sky, Jupiter is visible in the second half of the night throughout the month. You can observe it in the constellation Aries, about 15 degrees north of the celestial equator. In the wee hours of August 7-8, the Moon will pass a mere 3 degrees north of the giant planet, effectively confirming its identity.
A good pair of binoculars will reveal Jupiter’s four largest natural satellites: the Galilean moons Io, Europa, Ganymede and Callisto, in order of increasing distance from the planet. Observe Jupiter for three consecutive nights and you’ll notice the moons’ changing positions around the planet.
Jupiter’s atmosphere is also highly active. A telescope will allow you to glimpse the white and brownish cloud bands that encircle the giant planet, and an enormous storm system called the Great Red Spot. Don’t worry if it’s not visible when you take a look; simply try again the next day or the day after that, at the same time. Jupiter actually completes one full rotation in just 9 hours and 51 minutes, the fastest of any planet in the Solar System.
Undoubtedly one of the jewels of the night sky, Saturn will be in opposition in the early morning hours of August 27, as Earth sits between it and the Sun. This is the most favourable configuration for observing Saturn, since the distance separating us is the smallest it will get this year. “Smallest” is, of course, quite relative here: The lord of the rings currently lies about 1,310,930,000 km, or 73 light-minutes from Earth!
Saturn’s spectacular rings make it a plum target for curious observers with telescopes. The rings are tilted 9 degrees toward Earth, making it possible to observe a few details. Saturn shines in the constellation Aquarius this summer, 11 degrees below the celestial equator, and culminates only about 30 degrees high in the sky: Make sure you choose a location that offers an unobstructed view of the southern horizon.
The Perseid meteor shower—resulting from Earth crossing the stream of dust left behind by comet Swift-Tuttle—is one of the year’s most spectacular and certainly the most beloved in the Northern Hemisphere. When viewing conditions are ideal (no clouds, moon, light pollution, etc.), one can expect to see up to 100 meteors (or shooting stars) per hour, all appearing to originate from the same region of the sky: the constellation Perseus.
So, what can we expect in 2023? This year, peak activity is expected around 3 a.m. on August 13. Although this prediction can vary by several hours, the best time to admire the Perseids will definitely be the second half of the night of August 12-13. The constellation Perseus, where the radiant (area of sky from which the meteors seem to originate) is located, will be very high in the east—a prime position resulting in a much greater number of visible meteors. What’s more, the Moon won’t interfere with viewing, as it will be in its last crescent phase, just a few days before the new Moon on August 16. If you find yourself under cloudless skies, far enough away from light pollution, and have an open view of the sky, you should be able to spot more than 50 meteors per hour. If you’re unlucky and the weather is bad, the nights of August 11-12 and August 13-14 will also provide very good displays. You’ll also start seeing an uptick in the number of meteors starting from the second half of July until the end of August. Get your wish list ready!