This Week’s Sky at a Glance, August 12 – August 19

This weekend is the the annual Perseid meteor shower, which peaks on Saturday afternoon but it could delight patient stargazers throughout the weekend nights. You can see a few meteors per hour any night in a clear, dark sky, but the number increases when Earth passes through a trail of pebbles and dust left by a comet that makes frequent orbits around the Sun. The pebbles left by comet Swift-Tuttle in its 133-year orbit are quite large at a few centimetres, and they enter our atmosphere at a high relative velocity of 60 km/s (Earth travels at 30 km/s). Therefore, they can be very bright.

Meteors, also called shooting stars or falling stars, are the streaks of light created when particles enter the atmosphere at an altitude of about 100 kilometres. Those particles from comets disintegrate before they reach an altitude of 50 kilometres. Many meteors are faint and easily made invisible by moonlight and light pollution. This weekend the Moon is near third quarter and therefore it rises late in the evening, decreasing the number of visible meteors. But don’t fret; if the sky is clear there should be enough brighter ones to keep you entertained for a while. They will seem to be coming from a point, called the radiant, between the constellations Perseus and Cassiopeia. You should see more of them well after midnight when the radiant is high, but the evening Perseids tend to be long and bright.

Although a dark sky is preferred for watching meteors, many can still be enjoyed from an urban or suburban area. Get comfortable in a chair, have extra clothes or blankets if you plan to stay long as it can get very chilly, and select a patch of sky that is free of clouds and light. It is better to keep Perseus to your side rather than look in that direction because the meteors will look more spectacular, covering a longer distance. I recommend looking roughly northward so that the Moon is at your back. Be very happy if you see about 20 per hour on the peak night, or half that a day before or after. Anything more is a bonus.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 6:15 am and sunset will occur at 8:32 pm, giving 14 hours, 17 minutes of daylight (6:22 am and 8:35 pm in Saint John). Next Saturday the Sun will rise at 6:23 am and set at 8:20 pm, giving 13 hours, 57 minutes of daylight (6:30 am and 8:24 pm in Saint John).

The Moon is at third quarter on Monday, rising before midnight Sunday and setting around 1:40 pm Monday. It passes near Aldebaran on Wednesday morning and by Venus on August 19. Jupiter is sinking lower in the west at dusk, setting at 10:30 pm midweek and approaching Spica nightly. Saturn, in the southern sky in evening twilight, is the main telescopic attraction for the month. Venus is the bright Morning Star, rising around 3:15 am among the stars of Gemini. The Perseid meteor shower peaks on the afternoon of August 12 so look for increased meteor activity on all three nights and mornings this weekend. Ignore any Internet stories of this being the most spectacular meteor shower in recorded history

The Mount Carleton Star Party runs from August 11 – 12; a great place to spend the weekend taking nature hikes and catching shooting stars.

Questions? Contact Curt Nason using the form below.

[Featured image credit: Jared Tennant via Wikimedia]